Move WebAssemblyUtilities from Utils to the CodeGen library. It
primarily deals in MIR layer types, so it really lives in the CodeGen
Move a variety of other things around to try create better separation.
See issue #64166 for more info on layering.
I wasn't sure what to do with llvm/include/CodeGen/WasmAddressSpaces.h.
It has no other users, so it seems like it should live in lib/Target,
but it was just recently moved to CodeGen. I worked around the issue in
the Bazel build by adding it to the CodeGenTypes library, but this seems
awkard. Maybe it should live in BinaryFormat or IR.