[Coroutines] Handle lifetime markers, bitcast and unused instruciton for symmetric transfer

This fixes bug49888. The root cause for this is that
simplifyTerminatorLeadingToRet didn't handle lifetime markers well.
Another issue also noted in D116327 is that we deleted some inlined
optimization pass in CoroSplit so that simplifyTerminatorLeadingToRet
need to remove dead instructions by hand.

This patch fixes bug49888 by skipping lifetime markers and bitcast
instruction and removing dead instructions by hand in
simplifyTerminatorLeadingToRet.

Reviewed By: junparser

Differential Revision: https://reviews.llvm.org/D116330