This change prevents toolbar from updating when there is a transition happening to the view. This fixes the issue where header subviews would disappear when going back from a given screen. The root cause was that the config view manager would trigger subviews removal and re-layout itself. As aresult if we had a custom back button that back button would get removed and the title would move into its place while the screen animation is running. In order to prevent that we hook into View Manager's onDropViewInstance to notify header config that it is about to be destroyed. This in turn prevents any updates to be made to the toolbar config.
This change fixes the problem when header update would get triggered while the header config subviews are not yet fully unmounted. The root cause of this problem is kind of a mystery, I encouneter a crash when going back using back button from a screen that have custom back button image rendered. Turned out that after implementing removeAll schema the problem no longer occurs. I didn't have enough time to investigate it further but supporting removeAll schema is an improvement regardless so going with this solution for now.
When some of config props change or new header items are added we need to perform a header update. This diff adds logic to trigger updating header props when that happens.
A few bugs fixed with android native stack in this commit:
- fixed a problem with views not resizing when keyboard appears, the bug was due to onMeasure forwardin getHeight which was the old height of the container instead of the changed one
- fixed a problem with back button behavior not being consistent. Now back button is controlled by 'gestureEnabled' to emulate iOS behavior where there is no hw back button but you can swipe back instead.
- added compatibility for "contained" modal styles - for now we always render "containted" fragments on Android, plan to add a way to render in dialogs in the future
