This patch handles lowering of simple array assignment.
```
a(:) = 10
```
or
```
a(1) = 1
```
This patch is part of the upstreaming effort from fir-dev branch.
Reviewed By: PeteSteinfeld, schweitz
Differential Revision: https://reviews.llvm.org/D120501
Co-authored-by: Jean Perier <jperier@nvidia.com>
Co-authored-by: V Donaldson <vdonaldson@nvidia.com>
Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>
