[clang] [llvm] [clang] Implement JSON formatted -ftime-report (PR #137737)

[Arthur Eubanks via cfe-commits]

https://github.com/aeubanks approved this pull request.

lgtm, although I'd like @AaronBallman to take a quick look to make sure this seems ok (e.g. naming)

https://github.com/llvm/llvm-project/pull/137737