maintainVisibleContentPosition fixes on Android

[janicduplessis]

Summary:

We've noticed some cases of content jumping when using maintainVisibleContentPosition on Android when used for bidirectional pagination.

This makes some improvements to the maintainVisibleContent position implementation on Android to reduce cases of content jumping.

1. When using z-index Fabric re-orders the views so we can no longer rely on the ordering of the views to find the first visible view, we must go through all views and find the one that is bigger than the scroll position, but also has the smallest position.

2. This changes the approach to calculating the first visible view. Previously this was done in the Fabric willMountItems lifecycle, but there were cases where it would result in an incorrect update to the first visible view. Instead this changes the calculation to happen on scroll, which is actually when the first visible view can change.

3. This also does minor refactoring of the method names in MaintainVisibleScrollPositionHelper.java to better reflect the Fabric lifecycle names and what Android view lifecycle events they are called from.

Changelog:

[ANDROID] [FIXED] - maintainVisibleContentPosition fixes on Android

Test Plan:

Tested in the Expensify app to make sure this reduces cases of content jumping in the chats while scrolling and items are added at the start of the list on Android.