moveItem
Moves the MountItem associated to oldIndex in the newIndex position. This happens when a LithoView needs to re-arrange the internal order of its items. If an item is already present in newIndex the item is guaranteed to be either unmounted or moved to a different index by subsequent calls to either ComponentHost.unmount or ComponentHost.moveItem.
Parameters
item
The item that has been moved.
oldIndex
The current index of the MountItem.
newIndex
The new index of the MountItem.