CAPA-created subnet should have the "kubernetes.io/cluster/<clusterID>:" tag with "owned" value instead of "shared"

[r4f4]

/kind bug

What steps did you take and what happened:

Right now CAPA is applying the same "kubernetes.io/cluster/: shared" tag for subnets whether they are managed or unmanaged.

What did you expect to happen:

CAPA-created (managed) subnets should be tagged with "owned".

Anything else you would like to add:

The tag value itself shouldn't cause issues for CCM since it matches only on the tag Key: https://github.com/kubernetes/cloud-provider-aws/blob/master/pkg/providers/v1/aws.go#L1604-L1611

Environment:

• Cluster-api-provider-aws version:
• Kubernetes version: (use kubectl version):
• OS (e.g. from /etc/os-release):

[k8s-ci-robot]

This issue is currently awaiting triage.

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