[llvm] [BOLT][NFC] Add documentation on BOLT options (PR #92117)

[Maksim Panchenko via llvm-commits]

maksfb wrote:

@sjoerdmeijer Appreciate your feedback. Sometimes we forget how much external users we have. Regardless of the sync issue, @ElvinaYakubova 's documentation is a welcome addition.

https://github.com/llvm/llvm-project/pull/92117