* Fix setting root with bottomTabs.visible false
* Fix bottomTabs invisible after hiding through mergeOptions

on iOS, setting root with invisible bottomTabs doesn't work out of the box. We had to change the implementation and load the bottomTabsController children after it has been loaded to the window's rootViewController.

Fix an issue where bottomTab.testID doesn't get updated on mergeOptions unless a new UITabBarItem is created. Look like an issue in iOS where tabBarItem.accessibilityIdentifier doesn't get updated unless a new tabBarItem is created.

Refactor bottomTabs options applying mechanism. Both bottomTab and bottomTabs presenters were part of the base UIViewController class which was wrong. This commits moves them to the BottomTabsController.

This refactor mostly contains the following

* Detach bottomTabPresenter from basePresenter
* Create tabBarItem appearance on presenter init
* Refactor bottomTabPresenter
* Refactor bottomTabPresenter
* Move appearance creation to bottomTabsController
* Merge child options with direct child controller