E2E tests for AlternativeGCStrategy

[wyike]

What type of PR is this?
/kind support

What this PR does / why we need it:

Add two e2e for AlternativeGCStrategy feature

• [managed] [gc] should cleanup a cluster that has ELB/NLB load balancers using AlternativeGCStrategy
• [unmanaged] [gc] should cleanup a cluster that has ELB/NLB load balancers using AlternativeGCStrategy

They have exact same test steps with [managed] [gc] should cleanup a cluster that has ELB/NLB load balancers and [unmanaged] [gc] should cleanup a cluster that has ELB/NLB load balancers, except that before creating workload cluster, shared.ReconfigureDeployment is executed to reconfigure capa deployment with AlternativeGCStrategy feature flag set to true and will recover capa after test is done

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #4161

Special notes for your reviewer:

Checklist:

• squashed commits
• includes documentation
• adds unit tests
• adds or updates e2e tests

Release note:

Add E2E tests for AlternativeGCStrategy

[wyike]

/test pull-cluster-api-provider-aws-e2e-eks-gc

[Ankitasw]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Ankitasw

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