[Azure VMs Pool] Support mixed agentpool types in Azure Cache

[wenxuan0923]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Use Azure cache to track VMs pools. As of today, CAS can only be used for single type of agentpool - either vmss or standard. We need to support vms pool and mixed agentpool types (vmss + vms). During the cache generation, we will fetch all resources regardless of the vmType, and also track the vms pools using a set (implemented with golang map) so we can distinguish between vmss vm instances and vms instances.

More details in the PR targeting 1.29 release:
#6689

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

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

[k8s-ci-robot]

Hi @wenxuan0923. Thanks for your PR.

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[tallaxes]

LGTM. Note that we already reviewed the corresponding 1.29 PR (the feedback there has been addressed and incorporated here as well), already merged.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: tallaxes, wenxuan0923

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[tallaxes]

/ok-to-test

[tallaxes]

A little concerned about implications (including performance) of doing this always, unconditionally; something to watch out for during testing.