Fixes assertion that arose from bad FIR being constructed.

* Fix assertion strings.

* Fixes assertion that arose from bad FIR being constructed.

With the default member-wise component assignment, the LHS and RHS may
be compatible but distinct types. This change to lowering manages both
the LHS and RHS independently rather than assume the two types are
identical. This avoids creating bogus FIR and asserting/crashing in
codegen.

Update the tests with the member-wise copy code.

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

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

Reviewed By: jeanPerier

Differential Revision: https://reviews.llvm.org/D127297