[REF] component: mount: remove renderBeforeRemount option

Re-render the component all the time before remounting it, which
seems safer anyway.

In the test, we had to add a nextTick to wait for the changes to
be notified (before, we waited thanks to the additional call to
mount). If we don't do the nextTick, mount is called, and render
is called right after (before the promise returned by mount is
resolved). This scenario doesn't work right now (see #441).

Closes #381

tests/component/component.test.ts

@@ -4911,10 +4911,8 @@ describe("unmounting and remounting", () => {
     expect(fixture.innerHTML).toBe("<div>1</div>");
     widget.unmount();
     expect(fixture.innerHTML).toBe("");
+    await nextTick(); // wait for changes to be detected before remounting
     await widget.mount(fixture);
-    expect(fixture.innerHTML).toBe("<div>1</div>");
-    widget.unmount();
-    await widget.mount(fixture, true);
     expect(fixture.innerHTML).toBe("<div>3</div>");
   });
 });