Update widget tile if the url should change

[Half-Shot]

Fixes element-hq/element-integration-manager#116

The scalar token can arrive async after we've rendered a widget, which means we may need to change the URL of the app tile after this has happened. It felt reasonable to me to raise an event from the widget to the tile when this happens.

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• Sign-off given on the changes (see CONTRIBUTING.md).

[t3chguy]

This was specifically not done as it'd kick you out of conferences/forms etc if the widget takes a param which changes, e.g. theme combined with #12295

[Half-Shot]

Okay, then I think we probably need a way to raise the non-ready state so the tile isn't presented as ready until we have our URL.

[t3chguy]

This wants a test for the scalar token & the theme variable cases

[richvdh]

Moving to draft while this remains in progress