[llvm] [Bolt] Add a new hidden option to perf2bolt for testing purpose (PR #163785)

[Amir Ayupov via llvm-commits]

https://github.com/aaupov commented:

Some more thoughts on this functionality (not blocking but please consider as follow-up items):
1. A note on constructing MMapEvents and BranchEvents strings - see inline comment.
2. In the general case we also need task events and buildid-list output. We should include that into perf script input as well.
3. Extra profile support: basic samples and mem profile.
4. If all of the above is implemented, the functionality should be unified with `parsePerfData` as the input would be the same (except coming from a pre-parsed file).

https://github.com/llvm/llvm-project/pull/163785