librustc: De-`@mut` `CrateContext::symbol_hasher`.
librustc: Remove unused `TypeNames::find_name` function
librustc: Remove unused `TypeNames::type_names` table
librustc: De-`&mut` `TypeNames`
librustc: De-`@mut` the crate context's `do_not_commit_warning_issued`
librustc: De-`@mut` the crate context
librustc: De-`@mut` the `ast_ty_to_ty_cache`.
librustc: De-`@mut` the `enum_var_cache`
librustc: Remove `ty_param_defs` from the type context
librustc: De-`@mut` the adjustments table in the type context
librustc: De-`@mut` `provided_method_sources` in the type context
librustc: De-`@mut` `supertraits` in the type context
librustc: De-`@mut` the item variance map in the type context
librustc: De-`@mut` the `normalized_cache` in the type context
librustc: De-`@mut` `destructor_for_type` in the type context
librustc: De-`@mut` `resolve::Module::kind`
librustc: De-`@mut` `resolve::Module::populated`
librustc: De-`@mut` `resolve::Module::def_id`
librustc: De-`@mut` `resolve::Module::glob_count`
librustc: De-`@mut` `resolve::Module::resolved_import_count`