[flang] Lower adjustl and adjustr intrinsics

This patch adds lowering for the `adjustl` and `adjustr`
intrinsics.

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

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D121780



Co-authored-by: V Donaldson <vdonaldson@nvidia.com>
Co-authored-by: Jean Perier <jperier@nvidia.com>