[Flang] Lower sin, cos intrinsics

The intrinsic computes the sin, cosine values. By default they are lowered
to runtime calls to the pgmath library, for llvm lowering they are
lowered to llvm intrinsics. The generic and llvm lowering does not
lower floating point types with kind greater than 8, the llvm lowering
does not support the complex types.

This is part of the upstreaming effort from the fir-dev branch in [1].
[1] https://github.com/flang-compiler/f18-llvm-project

Reviewed By: clementval

Differential Revision: https://reviews.llvm.org/D122320



Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>