This PR renames the CODEOWNERS file to REVIEWERS and works with DrahtBot to leave a comment requesting a review.
Testing of the functionality was done on https://github.com/adamjonas/bitcoin-codeowners-sandbox/pulls.
~EDIT: after further testing of a fake organization, it appears that in order to be automatically tagged, the reviewer requires write level permissions. This is undocumented and will obviously close the circle of who can be tagged and so this PR reverts the addition of the file in #18949.~
~This removes a line not being parsed in the CODEOWNERS file introduced in #18949. While the pattern checked out using git ls-files, it is preventing the CODEOWNERS file from automatically tagging reviewers. For future modifications to this file, note that any line failing to parse causes the entire file to stop identifying codeowners.~
~I experimented in a sandbox repo to discover the offending line and this change appears to fix the problem.~