[flang] Lower date_and_time and cpu_time intrinsics

This patch lowers the `cpu_time` and the `date_and_time` instrinsics to
FIR and runtime calls.

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

Depends on D121704

Reviewed By: PeteSteinfeld

Differential Revision: https://reviews.llvm.org/D121705



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