[fir] Add fir reduction builder

This patch introduces a bunch of builder functions
to create function calls to runtime reduction functions.

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

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

Differential Revision: https://reviews.llvm.org/D114460

Reviewed By: awarzynski