[parallel-queries] Refactor away DepGraph::work_products to avoid shared mutable state #50500

DepGraph::work_products is a field that collects the object files cached during the current compilation session. This information (probably) does not need to live in the dep-graph as shared mutable state. Instead the information could be threaded through via return values and function parameters. An initial analysis suggest that the following functions need to be modified:

• rustc_incremental::persist::work_product::save_trans_partition()
• librustc_trans::back::write::copy_module_artifacts_into_incr_comp_cache()
• librustc_trans::back::write::OngoingCrateTranslation::join()
• rustc_incremental::persist::save::save_work_products()

cc @rust-lang/wg-compiler-performance