[WebAssembly] Remove unnecessary instructions after TRY marker placement
This removes unnecessary instructions after TRY marker placement. There
are two cases:
- end/end_block can be removed if they overlap with try/end_try and they have the same return types.
- br right before catch that branches to after end_try can be deleted.
Subscribers: sbc100, jgravelle-google, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D58591