Various UI test fixes (#370)

* Increase integration tests time limits again as they're still ocasionally failing

* Fixed NavigationRootCoordinator name in logs

* Refactor UI tests hierarchy and introduce new userFlowScreen

* Introduce a RoomTimelineControllerFactory so that it can be mocked in the UserFlow UI tests

* Start using a mock timeline controller for the UserSession flows

* Remove the WeakDictionary dependency and replce it with a plain NSMapTable in the BackgroundTaskService

* Allow multiple UITests screenshots per screen

* Prevent the view hierarchy changing when taking screenshots

* Add UserSessionScreen UI tests

* Fix label triaging workflow project identifier as per vector-im/element-ios/pull/7150

* Fix settings screen tests

* Fix roomPlainNoAvatar and roomEncryptedWithAvatar UI tests

* Fix modal server selection screen UI tests

* Fix bug report and login screen UI tests

* Fix text typing missing characters on UI tests

* Fix sliding sync configuration on integration tests

* Stop crashing if not finding a particular room through the MockClientProxy

UITests/Sources/__Snapshots__/Application/de-DE-iPad-9th-generation.userSessionScreen-1.png

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