Change so that var definitions can be a module's return value (#6504)

* Change so that var definitions can be a module's return value

* Change car wheel assembly to use the new return mechanism

* Add sim test

* Update output

* Update module docs

* Add safety check to only work with modules

* Fix to use updated keyword args

rust/kcl-lib/src/simulation_tests.rs

@@ -2240,6 +2240,28 @@ mod multi_transform {
     }
 }
 
+mod module_return_using_var {
+    const TEST_NAME: &str = "module_return_using_var";
+
+    /// Test parsing KCL.
+    #[test]
+    fn parse() {
+        super::parse(TEST_NAME)
+    }
+
+    /// Test that parsing and unparsing KCL produces the original KCL input.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn unparse() {
+        super::unparse(TEST_NAME).await
+    }
+
+    /// Test that KCL is executed correctly.
+    #[tokio::test(flavor = "multi_thread")]
+    async fn kcl_test_execute() {
+        super::execute(TEST_NAME, true).await
+    }
+}
+
 mod import_transform {
     const TEST_NAME: &str = "import_transform";