[IMP] app: rethrow errors that were not handled

This commit makes it so that when an error occurs in an owl app and none
of the registered error handlers are able to handle it, we rethrow the
error instead of just logging it to the console and swallowing it. This
allows users of owl to handle errors that happen in owl applications by
using event listeners for error and unhandledrejection events on the
window.

tests/components/basics.test.ts

@@ -1,5 +1,12 @@
 import { App, Component, mount, status, toRaw, useState, xml } from "../../src";
-import { elem, makeTestFixture, nextTick, snapshotEverything, useLogLifecycle } from "../helpers";
+import {
+  elem,
+  makeTestFixture,
+  nextAppError,
+  nextTick,
+  snapshotEverything,
+  useLogLifecycle,
+} from "../helpers";
 import { markup } from "../../src/runtime/utils";
 
 let fixture: HTMLElement;
@@ -208,14 +215,14 @@ describe("basics", () => {
       static template = xml`<div/>`;
     }
     let error: Error;
-    const prom = mount(Test, fixture);
+    const app = new App(Test);
+    const prom = app.mount(fixture);
     await Promise.resolve();
     fixture.remove();
-    try {
-      await prom;
-    } catch (e) {
-      error = e as Error;
-    }
+    prom.catch((e: Error) => (error = e));
+    await expect(nextAppError(app)).resolves.toThrow(
+      "Cannot mount a component on a detached dom node"
+    );
     expect(error!).toBeDefined();
     expect(error!.message).toBe("Cannot mount a component on a detached dom node");
     expect(console.warn).toBeCalledTimes(1);