Try to organize MachineVerifier tests

The Verifier is separate from the MachineVerifier, so move it to a
different directory. Some other verifier tests were scattered in
target codegen tests as well (although I'm sure I missed some). Work
towards using a more consistent naming scheme to make it clearer where
the gaps still are for generic instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354138 91177308-0d34-0410-b5e6-96231b3b80d8
33 files changed