[flang] Add test for allocatable on the caller side

This patch adds test for allocatable on the caller side.
Lowering for missing features is added as well.

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

Depends on D120746

Reviewed By: PeteSteinfeld, schweitz

Differential Revision: https://reviews.llvm.org/D120748



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