[InstCombine] Refactor foldSelectICmpAndOr to use `decomposeBitTestICmp` instead of bespoke logic

This is essentially NFC as the cases `decomposeBitTestICmp` covers
that weren't already covered explicitly, will be canonicalized into
the cases explicitly covered. As well the unsigned cases don't apply
as the `Mask` is not a power of 2.

That being said, using a well established helper is less bug prone and
if some canonicalization changes, will prevent regressions here.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D148744