[llvm] [AA] Consider read-only provenance capture for synchronization effects (PR #197157)

[Antonio Frighetto via llvm-commits]

https://github.com/antoniofrighetto approved this pull request.

LGTM. For a moment, I thought we would now be saying Ref for `%a` if we were also to return it, but that's indeed not the case...
```llvm
define ptr @malloc_escape_after_readonly_and_return(ptr %x, i64 %sz) {
  %a = call ptr @malloc(i64 %sz)
  ; atomic ops
  call void @escape(ptr captures(read_provenance) %a)
  ret ptr %a
}
```

https://github.com/llvm/llvm-project/pull/197157