[llvm] [InstCombine] Prepare foldLogOpOfMaskedICmps to handle trunc to i1. (NFC) (PR #122179)

[Andreas Jonson via llvm-commits]

andjo403 wrote:

Changed to only do the preparation to support trunc but do not move the call to a place where any of the values can be trunc so this is NFC now.
Also added decomposeBitTest that only takes a value where the trunc or other bit test can be matched in.

https://github.com/llvm/llvm-project/pull/122179