[LoopPeel] Peel loops with exits followed by an unreachable or deopt block

Added support for peeling loops with exits that are followed either by an
unreachable-terminated block or block that has a terminatnig deoptimize call.
All blocks in the sequence must have an unique successor, maybe except
for the last one.

Reviewed By: mkazantsev

Differential Revision: https://reviews.llvm.org/D110922