[flang] Lower numeric related instrinsics

This patch adds lowering for some numeric related
intrinsics:
- `exponent`
- `floor`
- `fraction`
- `mod`
- `modulo`
- `nint`
- `not`
- `product`

This patch is part of the upstreaming effort from fir-dev branch.

Reviewed By: PeteSteinfeld, schweitz

Differential Revision: https://reviews.llvm.org/D121828



Co-authored-by: Peter Steinfeld <psteinfeld@nvidia.com>
Co-authored-by: Jean Perier <jperier@nvidia.com>
Co-authored-by: mleair <leairmark@gmail.com>
Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>