[flang][runtime] Enable real/complex kind 10 and 16 variants of dot_product.

HasCppTypeFor<> used to evaluate to false always, so kind 10 and 16
variants of dot_product were not instantiated even though the host
supported 80- and 128-bit real and complex data types.
In addition, HAS_FLOAT128 was not enabling complex kind=16 variant
of dot_product. This is fixed now.

Note that the change for HasCppTypeFor<> may also affect other
functions such as matmul, i.e. kind 10 and 16 variants of them
may become available now (depending on the build host).

Differential Revision: https://reviews.llvm.org/D133051