feat: add support for kubernetes.azure.com/priority label

[matthchr]

This should be preferred over the scalesetpriority variant

Description

How was this change tested?

• Unit tests
• E2E tests: https://github.com/Azure/karpenter-provider-azure/actions/runs/24908854155 - I believe all 3 of these flakes are known issues

Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: #
• No

Release Note

[tallaxes]

LGTM. Something to consider for later (nothing blocking):

• Let's maybe update the 0006-requirements-and-labels.md with the new label? (And let's not forget the user-facing docs.)
• Do we need guidance on that capacity-type, scalesetpriority, and priority should not be mixed (unless the values agree) - or is it obvious? And maybe a preference? (capacity-type as canonical in Karpenter, unless one of the others needed for compatibility?)
• Wondering if we should look into surfacing “no instance types available” better (maybe with reason?) - as we introduce (more?) ways to have conflicting requirements ...

[matthchr]

Wondering if we should look into surfacing “no instance types available” better (maybe with reason?) - as we introduce (more?) ways to have conflicting requirements ...

Yeah this would be good to do for sure. I've had issues in the past where we ask for conflicting requirements and it's not that easy to figure out. I am not sure that this is really going to increase that chance much. There are lots of other ways we already have that result in this situation, but filed an issue for this here: #1657

Do we need guidance on that capacity-type, scalesetpriority, and priority should not be mixed (unless the values agree) - or is it obvious? And maybe a preference? (capacity-type as canonical in Karpenter, unless one of the others needed for compatibility?)

I will add it in the public docs.

Let's maybe update the 0006-requirements-and-labels.md with the new label? (And let's not forget the user-facing docs.)

Sent a PR for this