Revert "[WebAssembly][InstrEmitter] Foundation for multivalue call lowering"
This reverts commit 3ef169e586f4d14efe690c23c878d5aa92a80eb5. The
purpose of this commit was to allow stack machines to perform
instruction selection for instructions with variadic defs. However,
MachineInstrs fundamentally cannot support variadic defs right now, so
this change does not turn out to be useful.
Depends on D73927.
Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D73928