[flang][runtime] Enable more APIs in the offload build. (#75996)

This patch enables more numeric (mod, sum, matmul, etc.) APIs,
and some others.

I added new macros to disable warnings about using C++ STD methods
like operators of std::complex, which do not have __device__ attribute.
This may probably result in unresolved references, if the header files
implementation relies on libstdc++. I will need to follow up on this.