Handle account deletion from MAS in Element X immediately

### Your use case

#### What would you like to do?

When we delete the current account from Element X in MAS after clicking on the 'Manage account' option or we remove the current session, getting logged out should be immediate.

#### Why would you like to do it?

At the moment, this depends on the responses to network requests performed after the sessions/accounts have been deleted. This means in poor connectivity scenarios, it could take several seconds (I've seen >5s) to get logged out automatically.

#### How would you like to achieve it?

We could have some kind of callback URL we can intercept so we know the account has been deleted or the current session removed.

### Have you considered any alternatives?

Maybe send a request as soon we come back to the settings screen, which could make the timeout shorter, but would still not be instant when connectivity is an issue.

### Additional context

At least on Element X Android we're opening the MAS screen in a separate process using the custom browser tabs, so we don't have access to the underlying webview to intercept arbitrary URLs. If we add some, they should have a format compatible with the apps.

Start with the Element X Android flow from the “Manage account” option and settings screen into the MAS screen opened in a custom browser tab. Trace how account deletion and current-session removal are currently detected after returning, then define a callback format compatible with the apps and verify that logout occurs immediately without relying on later network responses.

Written by the indexing model from the issue text.