[DX] Fix PSV resource serialization

When writing this initially I missed including the resource stride.
This change adds the resources stride to the serialized value.

I've also extended the testing and error reporting around parsing PSV
information. This adds tests to verify that the reader produces
meaningful error messages for malformed DXContainer files, and a test
that verifies the resource stride is respected in the reader even if
the stride isn't an expected or known value (as would happen if the
format changes in the future).

This is part of #59479.

Reviewed By: bogner, bob80905

Differential Revision: https://reviews.llvm.org/D155143