[PassManager] Add pretty stack entries before P->run() call.

This patch adds PrettyStackEntries before running passes. The entries
include the pass name and the IR unit the pass runs on.

The information is used the print additional information when a pass
crashes, including the name and a reference to the IR unit on which it
crashed. This is similar to the behavior of the legacy pass manager.

The improved stack trace now includes:

Stack dump:
0.	Program arguments: bin/opt -loop-vectorize -force-vector-width=4 crash.ll
1.	Running pass 'ModuleToFunctionPassAdaptor' on module 'crash.ll'
2.	Running pass 'LoopVectorizePass' on function '@a'

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D120993