gccrs: nr: Properly resolve imports and modules in segments

gcc/rust/ChangeLog:

	* resolve/rust-early-name-resolver-2.0.cc (Early::finalize_rebind_import): Insert imports
	as possible glob containers.
	* resolve/rust-name-resolution-context.cc (NameResolutionContext::map_usage): Allow
	multiple mappings of the same usage.
	* resolve/rust-name-resolution-context.hxx: Properly handle imports and modules in segments.

gcc/testsuite/ChangeLog:

	* rust/compile/import_in_type_ns6.rs: New test.
	* rust/compile/import_in_type_ns7.rs: New test.