gccrs: Fix rebinding imports

gccrs: Fix rebinding imports

gcc/rust/ChangeLog:

	* resolve/rust-ast-resolve-item.cc
	(flatten_glob): Use Import class.
	(flatten_rebind): Likewise.
	(flatten_list): Likewise.
	(flatten): Likewise.
	(flatten_use_dec_to_paths): Likewise.
	(flatten_use_dec_to_imports): Likewise.
	(ResolveItem::visit): Likewise.
	(Import::add_prefix): New.
	(rust_flatten_nested_glob): Adjust test.
	(rust_flatten_glob): Likewise.
	(rust_flatten_rebind_none): Likewise.
	(rust_flatten_rebind): Likewise.
	(rust_flatten_rebind_nested): Likewise.
	(rust_flatten_list): Likewise.
	* resolve/rust-ast-resolve-item.h
	(class Import): New.

gcc/testsuite/ChangeLog:

	* rust/compile/use_2.rs: New test.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>