Add forced logout flow when the proxy is no longer available (#3458)

* 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

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

features/securebackup/impl/src/main/res/values-zh/translations.xml

@@ -38,7 +38,6 @@
   <string name="screen_recovery_key_confirm_error_content">"请重试以访问您的聊天备份。"</string>
   <string name="screen_recovery_key_confirm_error_title">"恢复密钥不正确"</string>
   <string name="screen_recovery_key_confirm_key_description">"如果您有安全密钥或安全短语，也可以用。"</string>
-  <string name="screen_recovery_key_confirm_key_label">"恢复密钥或密码"</string>
   <string name="screen_recovery_key_confirm_key_placeholder">"输入……"</string>
   <string name="screen_recovery_key_confirm_lost_recovery_key">"丢失了恢复密钥？"</string>
   <string name="screen_recovery_key_confirm_success">"恢复密钥已确认"</string>