run post-RA hazard recognizer pass late

Memory legalizer, waitcnt, and shrink  passes can perturb the instructions,
which means that the post-RA hazard recognizer pass should run after them.
Otherwise, one of those passes may invalidate the work done by the hazard
recognizer. Note that this has adverse side-effect that any consecutive
S_NOP 0's, emitted by the hazard recognizer, will not be shrunk into a
single S_NOP <N>. This should be addressed in a follow-on patch.

Differential Revision: https://reviews.llvm.org/D49288

llvm-svn: 337154