Allow omitting the k8s patch version in `azuremanagedcontrolplanes`

[felfa01]

/kind feature

Describe the solution you'd like
AKS allows to omit the patch version and thus defaulting to latest patch. When trying to configure this via CAPZ the following error is thrown:

Error: admission webhook "validation.azuremanagedcontrolplanes.infrastructure.cluster.x-k8s.io" denied the request: must be a valid semantic version

Support docs: https://learn.microsoft.com/en-us/azure/aks/supported-kubernetes-versions?tabs=azure-cli#alias-minor-version

[dtzar]

This is possible today in the current Go SDK we use as well as in ASO.
The problematic code is here.

Tagging @nojnhuh in case he wants to consider lighting this up in his PR.

[nojnhuh]

I think this would fit better as a change separate from #4069. This might be a bit more complicated than changing a regex since that value is currently shared in the templates between AzureManagedControlPlane spec.version and MachinePool spec.template.spec.version and I'm not sure if CAPI accepts MAJOR.MINOR versions there.

[LochanRn]

@nojnhuh how do we support this if we want ?

Should I raise a support request in CAPI ?

[nojnhuh]

I think bringing this up in CAPI makes the most sense to me. That may have already been discussed at some point, so it would be worth a quick look through the CAPI issue queue, Slack, and weekly meeting notes to see if that has been previously brought up.

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