gccrs: Add new check for contains_associated_types

gccrs: Add new check for contains_associated_types

We don't need to setup associated types when a trait does not contain any
associated types.

gcc/rust/ChangeLog:

	* typecheck/rust-tyty-bounds.cc (TypeBoundPredicate::contains_associated_types):
	Check if a type bound predicate contains assocated types.
	* typecheck/rust-tyty.h: Declare the above mentioned function.
	* typecheck/rust-hir-trait-resolve.cc: Use `contains_associated_types`
	function.