[flang] Fold intrinsic inquiry functions SAME_TYPE_AS() and EXTENDS_TYPE_OF()

When the result can be known at compilation time, fold it.
Success depends on whether the operands are polymorphic.
When neither one is polymorphic, the result is known and can
be either .TRUE. or .FALSE.; when either one is polymorphic,
a .FALSE. result still can be discerned.

Differential Revision: https://reviews.llvm.org/D125062