Description of your changes

This PR aims to clean up warnings observed in crossplane/crossplane#6043 by:

• Fixing "unknown field" warnings using the correct structs matching schemas.
• Suppressing "prefer a domain-qualified finalizer" until we properly migrate them to the suggested format.

Together with the accompanying PR in Crossplane, I could validate that former warnings disappeared with the changes here.

This PR introduces a new package, warning, with the warning.LoggingHandler implementing rest.WarningHandler interface. This supports deduplication just like the current handler Crossplane uses, but it also uses provided crossplane runtime logger so that warnings logged as structured logs* and also enables discarding logs matching provided regular expressions. I opted to put this into crossplane runtime since we may want to leverage it in other repositories, e.g. providers, as well.

I have:

• Read and followed Crossplane's contribution process.
• Run earthly +reviewable to ensure this PR is ready for review.
• Added or updated unit tests.
• Linked a PR or a docs tracking issue to document this change.
• Added backport release-x.y labels to auto-backport this PR.

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