Make tcx optional from StableMIR run macro and extend it to accept closures Change `run` macro to avoid sometimes unnecessary dependency on `TyCtxt`, and introduce `run_with_tcx` to capture use cases where `tcx` is required. Additionally, extend both macros to accept closures that may capture variables. I've also modified the `internal()` method to make it safer, by accepting the type context to force the `'tcx` lifetime to match the context lifetime. These are non-backward compatible changes, but they only affect internal APIs which are provided today as helper functions until we have a stable API to start the compiler.