[IMP] component/qweb: remove t-mounted directive

The t-mounted directive main goals can be achieved with hooks, in a
better and more intuitive way.

closes #308

tests/animations.test.ts

@@ -5,7 +5,6 @@ import {
   makeDeferred,
   makeTestFixture,
   makeTestEnv,
-  nextTick,
   patchNextFrame,
   renderToDOM,
   unpatchNextFrame
@@ -265,28 +264,6 @@ describe("animations", () => {
     expect(fixture.innerHTML).toBe("<div></div>");
   });
 
-  test("t-transition combined with t-mounted", async () => {
-    env.qweb.addTemplate(
-      "TestWidget",
-      `<div><span t-if="state.flag" t-mounted="f" t-transition="chimay">blue</span></div>`
-    );
-    class TestWidget extends Widget {
-      state = useState({ flag: false });
-      f() {}
-    }
-    const widget = new TestWidget(env);
-    widget.f = jest.fn();
-    await widget.mount(fixture);
-
-    patchNextFrame(cb => cb());
-    expect(widget.f).toHaveBeenCalledTimes(0);
-
-    widget.state.flag = true;
-    await nextTick();
-    expect(widget.f).toHaveBeenCalledTimes(1);
-    unpatchNextFrame();
-  });
-
   test("t-transition, remove and re-add before transitionend", async () => {
     expect.assertions(11);