gccrs: nr: Add modules to types NS

gcc/rust/ChangeLog:

	* util/rust-hir-map.cc (Mappings::insert_module_id): New function.
	(Mappings::is_module): Likewise.
	* util/rust-hir-map.h: Store a set of AST modules, declare functions for adding and
	retrieving them.
	* resolve/rust-toplevel-name-resolver-2.0.cc (TopLevel::visit): Insert modules in the type
	namespace and store them in mappings.
	* resolve/rust-late-name-resolver-2.0.cc (resolve_type_path_like): Error out when an
	expected type resolves to a module.
	* resolve/rust-name-resolution.h: Add empty Definition constructor.
	* resolve/rust-resolve-builtins.cc (find_builtin_node_id): New function.
	* resolve/rust-resolve-builtins.h: Declare it.

gcc/testsuite/ChangeLog:

	* rust/compile/mod_in_types_ns.rs: New test.
	* rust/compile/mod_in_types_ns2.rs: New test.