Add vms pool implementation in 1.27

[wenxuan0923]

What type of PR is this?

/kind feature

Optionally add one or more of the following kinds if applicable:

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What this PR does / why we need it:

Add implementation to support VMs pool autoscaling. It does not support GPU pool for now (will be handled later).
It is same with #6951, but for version 1.27

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

1. Add a new toggle EnableVMsAgentPool to guard the behavior for VMs pool - it is default to false (azure_config.go)
2. Send List AP request to AKS-RP for constructing cache for vms pool - this will make sure it works for VMs pool with 0 node. (azure_cache.go)
3. Add a generic NodeTemplate which supports both VMSS and VMs agentpool, it will be used for scaling up VMs pool with 0 node. Before this change, only VMSS instance can be used as node template. (azure_template.go)
4. Add implementation for VMs pool, it supports scaling up by sending PUT AP request to AKS, and scaling down through DELETE machines request. It will use Deallocate mode from the agentpool to decide whether to delete or deallocate vm. (azure_vms_pool.go)

Does this PR introduce a user-facing change?

NONE (change is guarded by a toggle enableVMsAgentPool which is default to false. No cx-facing change right now.)

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

[k8s-ci-robot]

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: wenxuan0923
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