[clang] [llvm] [llvm][NFC] Rework Timer.cpp globals to ensure valid lifetimes (PR #121663)

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macurtis-amd wrote:

> Thanks for working on this.
> 
> I have a couple of questions about inconsistent casing. Other than that, this looks reasonable to me. But I don't have a great deal of experience with this part of LLVM, so please wait for other reviewers.

@tarunprabhu Thanks for taking a look at this.

https://github.com/llvm/llvm-project/pull/121663