gccrs: Support for Sized builtin marker trait

gccrs: Support for Sized builtin marker trait

When implementing general bounds checking as part of unify calls, we did
not check associated types on bounds which lead to alot of missed error
checking. This now recursively checks the bounds and the associated types
with a decent error message. This also required us to implement the Sized
marker trait to keep existing test-cases happy.

Fixes #1725

Signed-off-by: Philip Herron <herron.philip@googlemail.com>
gcc/rust/ChangeLog:

	* typecheck/rust-hir-trait-reference.cc (TraitReference::clear_associated_types): make const
	(TraitReference::clear_associated_type_projections): new interface
	* typecheck/rust-hir-trait-reference.h:
	* typecheck/rust-hir-trait-resolve.cc (TraitResolver::resolve_trait): refactor
	(TraitItemReference::associated_type_reset): reset projections
	* typecheck/rust-hir-type-bounds.h:
	* typecheck/rust-hir-type-check-expr.cc (TypeCheckExpr::visit): fix bounds
	* typecheck/rust-tyty-bounds.cc (TypeBoundsProbe::TypeBoundsProbe): refactor into cc file
	(TypeBoundsProbe::Probe): refactor
	(TypeBoundsProbe::is_bound_satisfied_for_type): likewise
	(TypeBoundsProbe::assemble_sized_builtin): add builtin for Sized
	(TypeCheckBase::get_predicate_from_bound): refactor
	(TypeBoundPredicate::lookup_associated_type): refactor
	* typecheck/rust-tyty-subst.cc (SubstitutionRef::lookup_associated_impl)
	(SubstitutionRef::prepare_higher_ranked_bounds): new interface to clear hanging bounds
	(SubstitutionRef::monomorphize): refactor
	* typecheck/rust-tyty-subst.h:
	* typecheck/rust-tyty.cc (BaseType::get_locus): helper
	(BaseType::satisfies_bound): ensure bounds are satisfied and assoicated types
	(ParamType::ParamType): new field in constructor
	(ParamType::clone): update clone
	(ParamType::set_implicit_self_trait): new interface
	(ParamType::is_implicit_self_trait): likewise
	* typecheck/rust-tyty.h: cleanup
	* util/rust-hir-map.cc (Mappings::Mappings): builtin marker
	(Mappings::~Mappings): delete marker
	(Mappings::lookup_builtin_marker): lookup
	* util/rust-hir-map.h: update header

gcc/testsuite/ChangeLog:

	* rust/compile/issue-1725-1.rs: New test.
	* rust/compile/issue-1725-2.rs: New test.