[fir] Avoid slice with substr in fir.array_load, fir.array_coor and fir.array_merge_store

Substring information on slice operation has been added in D112441.
The operations fir.array_load, fir.array_coor and fir.array_merge_store can take
a slice but not with a substring. This patch add this check in their verifier.

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

Reviewed By: schweitz

Differential Revision: https://reviews.llvm.org/D112568