[llvm] [llvm-mca] Add bottle-neck analysis to JSON output. (PR #90056)

[Andrea Di Biagio via llvm-commits]

adibiagio wrote:

Have you looked at whether test failures reported by 
buildkite/github-pull-requests (https://buildkite.com/llvm-project/github-pull-requests/builds/65010 )are genuine ?

The following tests fail after your change:
```
   LLVM :: tools/llvm-mca/JSON/X86/views-custom-parameters.s
   LLVM :: tools/llvm-mca/JSON/X86/views-multiple-anonymous-regions.s
   LLVM :: tools/llvm-mca/JSON/X86/views-multiple-region.s
   LLVM :: tools/llvm-mca/JSON/X86/views.s
```

I wonder if some of the CHECK-NEXT should be re-generated after your change.

https://github.com/llvm/llvm-project/pull/90056