markdown: Track code block metadata in parser (#28543)

This allows us to not scan the codeblock content for newlines on every
frame in `active_thread`

Release Notes:

- N/A
44cb8e582bBennet Bo Fenner committed on 4/10/2025, 9:49:08 PM· committed by GitHubparent73305ce
3 files changedLine totals unavailable