Derive Var and Export for DynGd<T, D>

- Fix tests (make sure that all instances will be properly freed), move wrong type test to one that contains nothing but RefCounted instances

itest/godot/ManualFfiTests.gd

@@ -81,12 +81,17 @@ func test_export_dyn_gd():
 	var refc = RefcHealth.new()
 	dyn_gd_exporter.first = refc
 	assert_eq(dyn_gd_exporter.first, refc)
+	dyn_gd_exporter.free()
+	node.free()
+
+func test_export_dyn_gd_should_fail_for_wrong_type():
+	var dyn_gd_exporter = RcDynGdExporter.new()
+	var refc = RefcHealth.new()
 	disable_error_messages()
 	dyn_gd_exporter.second = refc # Should fail.
 	enable_error_messages()
 	assert_fail("DynGdExporter.second should only accept NodeHealth if it implements InstanceIdProvider trait")
 
-
 class MockObjGd extends Object:
 	var i: int = 0
 

itest/rust/src/object_tests/dyn_gd_test.rs

@@ -449,6 +449,13 @@ impl InstanceIdProvider for foreign::NodeHealth {
 // ----------------------------------------------------------------------------------------------------------------------------------------------
 // Check if DynGd can be properly exported
 
+#[derive(GodotClass)]
+#[class(init)]
+struct RcDynGdExporter {
+    #[var]
+    only_node_health: Option<DynGd<foreign::NodeHealth, dyn InstanceIdProvider>>,
+}
+
 #[derive(GodotClass)]
 #[class(base=Node)]
 struct DynGdExporter {