Data-parallel multi-core RT codegen

• Use prettyplease to auto-format generated RT Rust code.
• Refactor RT backend to allow for nested async closure environments.
• Lower fork, join, thread ID, and reduce nodes in RT backend (only ParallelFork and ParallelReduce nodes though!).
• QOL make sure there's an entry for start node in fork join nests.
• Add __RawPtrSendSync to hercules_rt and in generated RT code to move pointers across async boundaries.
• Re-schedule test6 in fork_join_tests to generate a tiled fork-join, half in RT code and half in CPU code to test multicore.