Combine PropertyGrid tab information. (#6108)

Combine tab related data into a record for clarity and safety. Use a List<> instead of an array to avoid complicated insert logic.

Maintain tab selection as an instance instead of an index.

Move error handling to CreateTab so thrown exceptions with messages (missing a bitmap / name for the tab) are actually thrown instead of a silent failure.

src/System.Windows.Forms/src/System/Windows/Forms/PropertyGrid.PropertyTabCollection.cs

@@ -35,7 +35,7 @@ public int Count
                         return 0;
                     }
 
-                    return _ownerPropertyGrid._viewTabs.Length;
+                    return _ownerPropertyGrid._tabs.Count;
                 }
             }
 
@@ -55,7 +55,7 @@ public PropertyTab this[int index]
                         throw new InvalidOperationException(SR.PropertyGridPropertyTabCollectionReadOnly);
                     }
 
-                    return _ownerPropertyGrid._viewTabs[index];
+                    return _ownerPropertyGrid._tabs[index].Tab;
                 }
             }
 
@@ -100,9 +100,14 @@ void ICollection.CopyTo(Array dest, int index)
                     return;
                 }
 
-                if (_ownerPropertyGrid._viewTabs.Length > 0)
+                if (_ownerPropertyGrid._tabs.Count > 0)
                 {
-                    Array.Copy(_ownerPropertyGrid._viewTabs, 0, dest, index, _ownerPropertyGrid._viewTabs.Length);
+                    Array.Copy(
+                        _ownerPropertyGrid._tabs.Select(i => i.Tab).ToArray(),
+                        0,
+                        dest,
+                        index,
+                        _ownerPropertyGrid._tabs.Count);
                 }
             }
 
@@ -116,7 +121,7 @@ public IEnumerator GetEnumerator()
                     return Array.Empty<PropertyTab>().GetEnumerator();
                 }
 
-                return _ownerPropertyGrid._viewTabs.GetEnumerator();
+                return _ownerPropertyGrid._tabs.Select(i => i.Tab).GetEnumerator();
             }
 
             public void RemoveTabType(Type propertyTabType)

src/System.Windows.Forms/src/System/Windows/Forms/PropertyGrid.TabInfo.cs

@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.ComponentModel;
+using System.Windows.Forms.Design;
+
+namespace System.Windows.Forms
+{
+    public partial class PropertyGrid
+    {
+        private record TabInfo(PropertyTab Tab, PropertyTabScope Scope, ToolStripButton Button)
+        {
+            public Type TabType => Tab.GetType();
+        }
+    }
+}