feat(elbv2): Implement IConnectable to NLB (#28494)

# Summary
Implement an `IConnectable` interface to a NetworkLoadBalancer. 

# Why need this change?
AWS CDK has great features for abstraction. `IConnectable` interface is one of this. `IConnectable` simplifies the management of security groups. AWS CDK add support security group to NLB at #27978. However, Currently NLB not implement `IConnectable`, so customers can't use useful interface in AWS CDK.

# Example use case

```ts
declare const lb: elbv2.NetworkLoadBalancer;
declare const asg: autoscaling.AutoScalingGroup;

asg.connections.allowFrom(lb, ec2.Port.tcp(8088)); // currently can not
```

Closes #26735

----

*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

packages/@aws-cdk-testing/framework-integ/test/aws-elasticloadbalancingv2/test/integ.nlb-lookup.js.snapshot/aws-cdk-elbv2-StackWithLb.template.json

@@ -18,9 +18,6 @@
   "VPCPublicSubnet1SubnetB4246D30": {
    "Type": "AWS::EC2::Subnet",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "AvailabilityZone": "test-region-1a",
     "CidrBlock": "10.0.0.0/18",
     "MapPublicIpOnLaunch": true,
@@ -37,21 +34,24 @@
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PublicSubnet1"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPublicSubnet1RouteTableFEE4B781": {
    "Type": "AWS::EC2::RouteTable",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "Tags": [
      {
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PublicSubnet1"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPublicSubnet1RouteTableAssociation0B0896DC": {
@@ -68,12 +68,12 @@
   "VPCPublicSubnet1DefaultRoute91CEF279": {
    "Type": "AWS::EC2::Route",
    "Properties": {
-    "RouteTableId": {
-     "Ref": "VPCPublicSubnet1RouteTableFEE4B781"
-    },
     "DestinationCidrBlock": "0.0.0.0/0",
     "GatewayId": {
      "Ref": "VPCIGWB7E252D3"
+    },
+    "RouteTableId": {
+     "Ref": "VPCPublicSubnet1RouteTableFEE4B781"
     }
    },
    "DependsOn": [
@@ -95,15 +95,15 @@
   "VPCPublicSubnet1NATGatewayE0556630": {
    "Type": "AWS::EC2::NatGateway",
    "Properties": {
-    "SubnetId": {
-     "Ref": "VPCPublicSubnet1SubnetB4246D30"
-    },
     "AllocationId": {
      "Fn::GetAtt": [
       "VPCPublicSubnet1EIP6AD938E8",
       "AllocationId"
      ]
     },
+    "SubnetId": {
+     "Ref": "VPCPublicSubnet1SubnetB4246D30"
+    },
     "Tags": [
      {
       "Key": "Name",
@@ -119,9 +119,6 @@
   "VPCPublicSubnet2Subnet74179F39": {
    "Type": "AWS::EC2::Subnet",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "AvailabilityZone": "test-region-1b",
     "CidrBlock": "10.0.64.0/18",
     "MapPublicIpOnLaunch": true,
@@ -138,21 +135,24 @@
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PublicSubnet2"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPublicSubnet2RouteTable6F1A15F1": {
    "Type": "AWS::EC2::RouteTable",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "Tags": [
      {
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PublicSubnet2"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPublicSubnet2RouteTableAssociation5A808732": {
@@ -169,12 +169,12 @@
   "VPCPublicSubnet2DefaultRouteB7481BBA": {
    "Type": "AWS::EC2::Route",
    "Properties": {
-    "RouteTableId": {
-     "Ref": "VPCPublicSubnet2RouteTable6F1A15F1"
-    },
     "DestinationCidrBlock": "0.0.0.0/0",
     "GatewayId": {
      "Ref": "VPCIGWB7E252D3"
+    },
+    "RouteTableId": {
+     "Ref": "VPCPublicSubnet2RouteTable6F1A15F1"
     }
    },
    "DependsOn": [
@@ -196,15 +196,15 @@
   "VPCPublicSubnet2NATGateway3C070193": {
    "Type": "AWS::EC2::NatGateway",
    "Properties": {
-    "SubnetId": {
-     "Ref": "VPCPublicSubnet2Subnet74179F39"
-    },
     "AllocationId": {
      "Fn::GetAtt": [
       "VPCPublicSubnet2EIP4947BC00",
       "AllocationId"
      ]
     },
+    "SubnetId": {
+     "Ref": "VPCPublicSubnet2Subnet74179F39"
+    },
     "Tags": [
      {
       "Key": "Name",
@@ -220,9 +220,6 @@
   "VPCPrivateSubnet1Subnet8BCA10E0": {
    "Type": "AWS::EC2::Subnet",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "AvailabilityZone": "test-region-1a",
     "CidrBlock": "10.0.128.0/18",
     "MapPublicIpOnLaunch": false,
@@ -239,21 +236,24 @@
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PrivateSubnet1"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPrivateSubnet1RouteTableBE8A6027": {
    "Type": "AWS::EC2::RouteTable",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "Tags": [
      {
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PrivateSubnet1"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPrivateSubnet1RouteTableAssociation347902D1": {
@@ -270,21 +270,18 @@
   "VPCPrivateSubnet1DefaultRouteAE1D6490": {
    "Type": "AWS::EC2::Route",
    "Properties": {
-    "RouteTableId": {
-     "Ref": "VPCPrivateSubnet1RouteTableBE8A6027"
-    },
     "DestinationCidrBlock": "0.0.0.0/0",
     "NatGatewayId": {
      "Ref": "VPCPublicSubnet1NATGatewayE0556630"
+    },
+    "RouteTableId": {
+     "Ref": "VPCPrivateSubnet1RouteTableBE8A6027"
     }
    }
   },
   "VPCPrivateSubnet2SubnetCFCDAA7A": {
    "Type": "AWS::EC2::Subnet",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "AvailabilityZone": "test-region-1b",
     "CidrBlock": "10.0.192.0/18",
     "MapPublicIpOnLaunch": false,
@@ -301,21 +298,24 @@
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PrivateSubnet2"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPrivateSubnet2RouteTable0A19E10E": {
    "Type": "AWS::EC2::RouteTable",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "Tags": [
      {
       "Key": "Name",
       "Value": "aws-cdk-elbv2-StackWithLb/VPC/PrivateSubnet2"
      }
-    ]
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
    }
   },
   "VPCPrivateSubnet2RouteTableAssociation0C73D413": {
@@ -332,12 +332,12 @@
   "VPCPrivateSubnet2DefaultRouteF4F5CFD2": {
    "Type": "AWS::EC2::Route",
    "Properties": {
-    "RouteTableId": {
-     "Ref": "VPCPrivateSubnet2RouteTable0A19E10E"
-    },
     "DestinationCidrBlock": "0.0.0.0/0",
     "NatGatewayId": {
      "Ref": "VPCPublicSubnet2NATGateway3C070193"
+    },
+    "RouteTableId": {
+     "Ref": "VPCPrivateSubnet2RouteTable0A19E10E"
     }
    }
   },
@@ -355,11 +355,27 @@
   "VPCVPCGW99B986DC": {
    "Type": "AWS::EC2::VPCGatewayAttachment",
    "Properties": {
-    "VpcId": {
-     "Ref": "VPCB9E5F0B4"
-    },
     "InternetGatewayId": {
      "Ref": "VPCIGWB7E252D3"
+    },
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
+    }
+   }
+  },
+  "SGADB53937": {
+   "Type": "AWS::EC2::SecurityGroup",
+   "Properties": {
+    "GroupDescription": "aws-cdk-elbv2-StackWithLb/SG",
+    "SecurityGroupEgress": [
+     {
+      "CidrIp": "0.0.0.0/0",
+      "Description": "Allow all outbound traffic by default",
+      "IpProtocol": "-1"
+     }
+    ],
+    "VpcId": {
+     "Ref": "VPCB9E5F0B4"
     }
    }
   },
@@ -374,6 +390,14 @@
     ],
     "Name": "my-load-balancer",
     "Scheme": "internet-facing",
+    "SecurityGroups": [
+     {
+      "Fn::GetAtt": [
+       "SGADB53937",
+       "GroupId"
+      ]
+     }
+    ],
     "Subnets": [
      {
       "Ref": "VPCPublicSubnet1SubnetB4246D30"
@@ -414,12 +438,12 @@
    "Properties": {
     "Port": 443,
     "Protocol": "TCP",
+    "TargetType": "ip",
     "Targets": [
      {
       "Id": "10.0.1.1"
      }
     ],
-    "TargetType": "ip",
     "VpcId": {
      "Ref": "VPCB9E5F0B4"
     }
@@ -443,6 +467,28 @@
     "Name": "TgArn"
    }
   },
+  "SgId": {
+   "Value": {
+    "Fn::GetAtt": [
+     "SGADB53937",
+     "GroupId"
+    ]
+   },
+   "Export": {
+    "Name": "SgId"
+   }
+  },
+  "ExportsOutputFnGetAttSGADB53937GroupId97E49F2D": {
+   "Value": {
+    "Fn::GetAtt": [
+     "SGADB53937",
+     "GroupId"
+    ]
+   },
+   "Export": {
+    "Name": "aws-cdk-elbv2-StackWithLb:ExportsOutputFnGetAttSGADB53937GroupId97E49F2D"
+   }
+  },
   "ExportsOutputRefLB8A12904C1150D6A6": {
    "Value": {
     "Ref": "LB8A12904C"