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

[Alan Zhao via cfe-commits]

alanzhao1 wrote:

@aeubanks this PR doesn't implement redirecting the output to a file, but I figured I'd implement that in another PR to keep things organized.

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