Some refactoring of the rust generated code

Always use a Pin<Rc> for the component. (This is required to support repeater
within repeater as well anyway)
Do not use the context within the binding. We can get along by simply capturing
a weak pointer to the component

examples/rustwasmtest/src/lib.rs

@@ -10,5 +10,5 @@ pub fn wasm_main() {
     #[cfg(debug_assertions)]
     console_error_panic_hook::set_once();
 
-    Hello::default().run();
+    Hello::new().run();
 }