More fixes to the handling of CVR-comparisons on array types. Adds a method to

QualType to get CVR-qualifiers through array types, and switches the primary
comparison methods to use it. This may allow simplifying some of the callers of
getUnqualifiedArrayType.

Also fix the normalizing of CV-qualification during template deduction to
normalize through arrays and allow a more qualified deduced array type. This
fixes PR5911.

llvm-svn: 92289