[TableGen] Resolve complex def names inside multiclasses

[TableGen] Resolve complex def names inside multiclasses

We had not been trying hard enough to resolve def names inside multiclasses
that had complex concatenations, etc. Now we'll try harder.

Patch by Amaury Sechet!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237877 91177308-0d34-0410-b5e6-96231b3b80d8