Fix a deadlock between WindowManagerGlobal and WindowManagerService

When a new display added, would first lock WMS then create a new
DisplayContent, that would also create the corresponding
SystemGesturesPointerEventListener, GestureDetector, ViewConfiguration,
and WindowManagerImpl, and it would also temporarily lock
WindowManagerGlobal in WindowManagerImpl's constructor.

This patch would post creating GestureDetector to avoid the deadlock
caused by other thread also lock WMS/WindowMaagerGlobal at same time.

Bug: 132746553
Test: create a app with splash screen and connect to new display at same
      time.
Change-Id: I246e596dff387923356bbc579f785b634d3d2468