fix(logql): A renamed label should use ParsedLabel category to take precendence

[ashwanthgoli]

What this PR does / why we need it:

Renaming labels using label_format dst=src is broken on main. Destination label does not appear in the resulting label set if the source is a stream label. This is because we don't append the labels from add[StreamLabel] list to the resulting buffer, this looks like a conscious choice to not pollute StreamLabels.

I felt the correct fix here is to correctly tag the renamed label as a ParsedLabel. This also makes sure the new label supersedes any structured metadata if present.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Checklist

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• Documentation added
• Tests updated
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[loki-gh-app]

This PR must be merged before a backport PR will be created.