Copy utilities updated and added for MI flags
Summary: This patch adds a GlobalIsel copy utility into MI for flags and updates the instruction emitter for the SDAG path. Some tests show new behavior and I added one for GlobalIsel which mirrors an SDAG test for handling nsw/nuw.
Reviewers: spatel, wristow, arsenm
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D52006