[clang] Add a raw_ostream operator<< overload for QualType

[clang] Add a raw_ostream operator<< overload for QualType

Under the hood this prints the same as `QualType::getAsString()` but cuts out the middle-man when that string is sent to another raw_ostream.

Also cleaned up all the call sites where this occurs.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D123926