Default min/max sizes for Azure VMSSs

[rrangith]

Which component are you using?:

cluster-autoscaler

Is your feature request designed to solve a problem? If so describe the problem this feature should solve.:
Currently if a VMSS is missing a min or max tag it will be ignored by CA.

autoscaler/cluster-autoscaler/cloudprovider/azure/azure_manager.go

Lines 334 to 351 in cf606a1

	if spec.MinSize < 0 {
	klog.Warningf("ignoring vmss %q because of minimum size must be a non-negative number of nodes", *scaleSet.Name)
	continue
	}
	if val, ok := scaleSet.Tags["max"]; ok {
	if maxSize, err := strconv.Atoi(*val); err == nil {
	spec.MaxSize = maxSize
	} else {
	klog.Warningf("ignoring vmss %q because of invalid maximum size specified for vmss: %s", *scaleSet.Name, err)
	continue
	}
	} else {
	klog.Warningf("ignoring vmss %q because of no maximum size specified for vmss", *scaleSet.Name)
	continue
	}
	if spec.MaxSize < spec.MinSize {
	klog.Warningf("ignoring vmss %q because of maximum size must be greater than minimum size: max=%d < min=%d", *scaleSet.Name, spec.MaxSize, spec.MinSize)
	continue

Azure has a limit of 50 tags per resource https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/tag-resources#limitations. So these 2 tags take up valuable tag slots.

If a user is fine with the VMSS using a default value for min/max, they could omit the min/max tags and instead use the default

Describe the solution you'd like.:

Maybe a way to configure a min/max through autodiscovery, 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` "+

Describe any alternative solutions you've considered.:

An alternative solution is just to default the min to 0 #6858

This would save 1 tag

Additional context.: