Reland "[web] Turn on CanvasKit Chromium (#40459)"

[mdebbar]

Original PR: #40459
Revert PR: #40495

We had to put back image codecs into CanvasKit Chromium (#40501) before relanding this.

Copied from the original PR:

---

This is the last bit to make CanvasKit Chromium available to our users by default.

Users can always opt-out by canvasKitVariant: "full" to their runtime configuration similar to this.

_flutter.loader.loadEntrypoint({
  onEntrypointLoaded: async function(engineInitializer) {
    let appRunner = await engineInitializer.initializeEngine({
      canvasKitVariant: "full",
    });

    await appRunner.runApp();
  }
});

Closes flutter/flutter#122329