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

[Alan Zhao via cfe-commits]

alanzhao1 wrote:

The buildkite failure can be ignored; the offending test (Unwind/split-machine-functions.test) also fails on `main` (or rather the parent commit of this PR's branch).

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