✨ cli: write diagnostics in kubectl-workspace to stderr

[embik]

Summary

While working on https://github.com/embik/kubectl-switch-ws I noticed that kubectl-workspace use will always print diagnostic information (deprecation notices and warnings about unfinished API bindings), even when using --short for inclusion in scripts / terminal prompts. There is no good way to avoid these warnings for scripts that only expect the workspace name returned as output.

I would like to propose that we start writing this supplementary information to stderr, which is specifically for diagnostic information and errors. This way, scripts can avoid the warnings by using something like kubectl workspace use --short <workspace> 2>/dev/null to make sure you only get back the workspace name (or an exit code that isn't zero, which signals that something bad happened).

There's also an old OWNERS file left here which I'd propose to remove.

Related issue(s)

Fixes #

Release Notes

Write diagnostics (deprecation notices and warnings) in `kubectl-workspace` to stderr instead of stdout

[embik]

/cc @mjudeikis @sttts

[mjudeikis]

Where I dont quite like abusing stderr but I dont see better way without having bunch of
if short; dont print and this sound more of the evil compared to what you propose.
/lgtm
/approve
/hold

[kcp-ci-bot]

LGTM label has been added.

Git tree hash: 8cc6a3bd49750ad6bf093e2440f06617f9a45927

[sttts]

/lgtm
/approve

[kcp-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mjudeikis, sttts

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[embik]

/hold cancel

[embik]

/kind cleanup