[Clang] Update typechecking of builtin elementwise ternary math operators (#155620)
For scalars we directly compare their unqualified types. But even if we
compare unqualified vector types, a difference in qualifiers in the
element types can make the vector types be considered not equal. For
example, vector of 4 'const float' values vs vector of 4 'float' values.
So we compare unqualified types of their elements and number of
elements.
Fixes #155405