Default Azure VMSS min size to 0 if not provided

[rrangith]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Currently the autoscaler will ignore a VMSS if no min size is provided. This PR changes the behaviour so it will instead default to 0. This is a safe minimum and will allow VMSS's without a min tag to be considered.

Azure has a limit of 50 tags per resource https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/tag-resources#limitations. This change will allow people to save 1 tag space if they are ok with the default of 0.

Alternatives Considered

An alternative approach to this problem is having a min and max as part of the autodiscovery tags, similar to how GCP does it

autoscaler/cluster-autoscaler/main.go

Line 182 in cf606a1

"GCE matches by IG name prefix, and requires you to specify min and max nodes per IG, e.g. `mig:namePrefix=pfx,min=0,max=10` "+

. The min and max could be optional for Azure and used as default values if a VMSS is missing its min/max tags

Here is the alternative PR #6863

Does this PR introduce a user-facing change?

Default Azure VMSS min size to 0 if not provided

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

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[rrangith]

/assign @jackfrancis @feiskyer

I presented this at the SIG Autoscaling meeting and they suggested I reach out to you. Can I please get a review?

[gandhipr]

Would suggest default as 1. Can remove code that ignores vmss creation if min-size not provided.

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PR needs rebase.

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/lifecycle stale

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all PRs.

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/lifecycle rotten

[rrangith]

closing in favour of #6863