[docs] Cherrypick doc changes to docs/external/ files (#35948)

Various changes for the v24.2 release that did not make the cut. (OSS
files coming in separately)

NOTE: This required a manual conflict resolution due to the refactoring
of mojo/changelog.md and changelog-release.md, which was not accounted
for in [Internal Link]

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Co-authored-by: Arthur Evans <[email protected]>
Co-authored-by: Nick Kreeger <[email protected]>
Co-authored-by: Jack Clayton <[email protected]>
Co-authored-by: modularbot [Internal Link]

modular-orig-commit: a1f3c94fab6f75774e74b5184289633fe24ffe82

Author: scottamain