cloud-provider: update docs and guidance for InstanceV2 and Zones

[andrewsykim]

Signed-off-by: Andrew Sy Kim kim.andrewsy@gmail.com

What type of PR is this?
/kind documentation

What this PR does / why we need it:
Updates docs and guidance on cloud provider InstancesV2 and Zones interface for external cloud providers:

• removes experimental warning for InstancesV2
• document that implementation of InstancesV2 will disable calls to Zones
• deprecate Zones in favor of InstancesV2

In #93569 we updated the InstanceMetadata hook to include zone/region information for a node. This made sense because almost always you can retrieve zone/region information for an instance using the same API calls you would when registering the node. This reduces the number of API calls the cloud provider has to make to register a node.

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Updates docs and guidance on cloud provider InstancesV2 and Zones interface for external cloud providers:
* removes experimental warning for InstancesV2
* document that implementation of InstancesV2 will disable calls to Zones
* deprecate Zones in favor of InstancesV2

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[andrewsykim]

/triage accepted

[andrewsykim]

/assign @cheftako @cici37

[cheftako]

/lgtm
/approve

[cheftako]

/test pull-kubernetes-node-e2e

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: andrewsykim, cheftako

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[cici37]

/lgtm