Previously, the commit SHAs and PR numbers referenced in the generated
`CHANGELOG.md` were not automatically converted to links in the GitHub
UI (as happens for release notes and issue/PR comments). This made it
less straight-forward for someone reading the changelog to get to the
commit/PR corresponding to a change.
This commit updates the tooling that generates the changelog to convert
the commit SHA and the corresponding PR number (referenced at the end of
the commit message header) to links.
PR Close#42732