Add remaining repository User Timings for full content, commit and codeowners

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!267455 adds timings for the first file-tree row and the first highlighted code. The rest of #402772 is still open: full-list and full-file rendering, Show commit and Show codeowners.

The full-content timings need an agreed end point first, cause rows and chunks only render when they scroll into view, so the last one depends on the screen size.

From the review on !267455 (comment 4161159531)