* Add `MatrixClient.isSlidingSyncProxySupported` function
* Update localazy strings
* Modify `ErrorDialog` to have an `onSubmit` call, which will be used for the submit action.
Also make the title text optional and dismissing the dialog by tapping outside/going back configurable.
* Check if a forced migration to SSS is needed because the proxy is no longer available.
In that case, display the non-dismissable dialog and force the user to log out after enabling SSS.
* Enable native/simplified sliding sync by default.
* Refactor the login to make sure we:
1. Always try native/simplified sliding sync login first, if available.
2. Then, if it wasn't available or failed with an sliding sync not supported error, try with the proxy instead (either discovered proxy or forced custom one).
* Move logic to `LoggedInPresenter` and the UI to `LoggedInView`
* Update screenshots
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Co-authored-by: ElementBot <benoitm+elementbot@element.io>
