[WIP] Add script to verify build tags

[cblecker]

What this PR does / why we need it:
Adds a script to verify build tags are only present in files with a proper extension.

This doesn't yet fix all the files that are non-conformant, and is a work in progress.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #55750

Release note:

NONE

[k8s-github-robot]

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[BenTheElder]

/retest

[BenTheElder]

I'd like to tighten up cross this week so we can avoid more unnecessary breakage going into 1.9, this PR is SGTM for that.

[k8s-ci-robot]

@cblecker: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
pull-kubernetes-verify	f67e070	link	/test pull-kubernetes-verify

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[cblecker]

Closing in favour of #59289