[flang][NFC] Add more test cases for the array-value-copy pass

This patch adds some test cases for the array-value-copy pass with slices.

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

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D122807



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