Eliminate duplicated code between render passes and render bundles

[andyleiserson]

Render passes and render bundles implement many of the same operations, but with enough differences in the implementation that it is not trivial to reuse the same code. Even though it will require some effort to reuse the same code, it is probably worth it, because there is a risk that code changes that should apply to both passes and bundles are made in only one place.

In #7911, I added some comments to on set_vertex_buffer and set_index_buffer noting this duplication.

#8038 notes a particular case where render bundles are missing validation that is present for render passes.