[ODRHash] Hash type-as-written

Close https://github.com/llvm/llvm-project/issues/63947
Close https://github.com/llvm/llvm-project/issues/63595

This is suggested by @rsmith in
https://reviews.llvm.org/D154324#inline-1508868

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D156210