Add iOS support for `bottomTabs.attachMode`.
This property controls when BottomTabs children are attached to hierarchy and when their React views are created.

By default, RNN attaches all children at the same time which might impact loading time as a few screens are instantiated at once.
Using `afterInitialTab` or `onSwitchToTab` generally leads to improved start up time.

* Set  as default modalPresentationStyle

* Sets the system default modalPresentationStyle

* Fix tests

* Fix unit tests

* Fix unit tests

* Add modal.swipeToDismiss option

* Migrate project to workspace

This commit moves all unit tests to the playground workspace

* Fix ios unit tests

* Build pods before testing

* Build typescript before running iOS tests

* Remove xcode 10 support