[llvm] [NFC][InstrProf] Rename internal `InstrProfiling` to `InstrLowerer` (PR #75139)

[Mircea Trofin via llvm-commits]

mtrofin wrote:

Ugh... @bogner just saw now @MaskRay added you. I pressed the merge button after @kazutakahirata LGTM-ed, if you have feedback on the name, please let me know and I'll happily update.

I was planning to rename the files to something like InstrProfileLoweringPass.h/.cpp, but I'll hold off if there is a longer discussion on names.

https://github.com/llvm/llvm-project/pull/75139