Update source links in admin api refs & elsewhere

[mDuo13]

Last PR for fixing source links in English files, continuing from #3364, #3365, and #3370.

• Update source code links for admin API method references, peer port method references, and a couple other places that weren't addressed yet.
• Remove deprecated frontmatter fields for many modified files.
• Make indentation more consistent in several example responses.
• Other minor cleanup in the modified files, like removing notes of things updated long ago.

There are still at least ~179 links in 117 translated files (ES, JA) that still need to be updated, but those should follow the changes in the English versions.