[llvm] [BOLT] Add itrace aggregation for AUX data (PR #70426)

[Amir Ayupov via llvm-commits]

aaupov wrote:

> > Question for reviewers: Do any Bolt tests run Bolt and pass in a perf.data file and check the .fdata is correct?
> 
> 
> 
> We have several internal tests for `perf2bolt`, but nothing in open source. @aaupov, is there a plan to port those?

Noted. I didn't port those as we had to sanitize inputs and perf data is tricky since it's opaque and captures a lot of system information by default. We do have some perf2bolt tests in rafaelauler/bolt-tests repo, but not a comprehensive suite.

CC @lanza 

https://github.com/llvm/llvm-project/pull/70426