[WebAssembly][NFC] Remove WebAssemblyStackifier TableGen backend

Summary:
Replace its functionality with a TableGen InstrInfo relational
instruction mapping. Although arguably more complex than the TableGen
backend, the relational mapping is a smaller maintenance burden than a
TableGen backend.

Reviewers: aardappel, aheejin, dschuff

Subscribers: mgorny, sbc100, jgravelle-google, sunfish, llvm-commits

Differential Revision: https://reviews.llvm.org/D53307

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344962 91177308-0d34-0410-b5e6-96231b3b80d8
10 files changed