[flang] Lower min|max intrinsics

This patch adds lowering for the following intrinsics:
- `max`
- `maxloc`
- `maxval`
- `minloc`
- `minval`

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

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D121701



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