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

• [x] Added tests that cover your change (if possible)
• [x] Added/modified documentation as required (such as the README.md, or the docs directory)
• [ ] Manually tested
• [x] 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?! :exploding_head:

• [ ] Backfilled missing tests for code in same general area :tada:
• [ ] Refactored something and made the world a better place :star2:

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: alebedev87 Once this PR has been reviewed and has the lgtm label, please assign johngmyers for approval. For more information see the Kubernetes Code Review Process.

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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.

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[alebedev87]

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

[k8s-ci-robot]

PR needs rebase.

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[k8s-triage-robot]

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