Non-breaking feature: create vpc objects in explicitly provided availability zones

[healthy-pod]

What type of PR is this?

/kind feature

What this PR does / why we need it:

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 #4333, continues the work started by @Skarlso in this #4543 by:

• moving the defaults for AvailabilityZoneSelection and AvailabilityZoneUsageLimit into defaulting webhooks instead of CRDs
• adding check in validating webhooks for conflicting use of AvailabilityZoneUsageLimit and AvailabilityZoneSelection with AvailabilityZones

Special notes for your reviewer:

Checklist:

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

Release note:

Ability to specify Availability Zones from spec.network.vpc in AWSManagedControlPlane, AWSCluster and AWSClusterTemplate CRDs.

[linux-foundation-easycla]

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