subnet discovery: new flag to enable prioritization by availability-zone locale

[alebedev87]

Issue

N/A

Description

Draft PR to gather opinions about adding a flag to enable different algorithms for the subnet selection from multiple qualified ones when they all come from the same availability zone. The sorting by subnet IDs remains the default. A new sorting alogrithm azfirst is added to prioritize availability-zone locale over other locales. This change may help to reduce the random aspect of the subnet selection when multiple locales are used in a cluster.

Example of where this can be helpful:

• AZ1: has availability-zone an outpost subnets, all tagged with cluster and role tags, so all eligible for the discovery
• AZ2: has only availability-zone subnets also tagged for the subnet discovery
• The discovery may fail with "subnets in multiple locales" error if outposts subnets from AZ1 have lower subnet IDs

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the docs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: alebedev87
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[k8s-ci-robot]

Hi @alebedev87. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[alebedev87]

@M00nF1sh @oliviassss: what do you think about this proposal?

[k8s-ci-robot]

PR needs rebase.

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