Support IME Window to show in secondary display.

1) Moving WMS.setInputMethodWindowLocked to DisplayContent,
   each display can have its own IME window.
2) Add getDisplayIdFromWindow in WindowManagerInternal,
   used for InputMethodManagerService to know which display
   for given IME window token.
3) Support add / remove IME window according displayId.
4) Modify WMS.inputMethodClientHasFocus to traverse all active display
   if inputMethodClient focused.
5) Add displayId parameter for IInputMethod.initializeInternal to
   update context display then client can addView to right display.

Note: 1) There should be zero behavior difference as long as the target
         app is running on the default display.
      2) The current implementation is not final and there are still
         chances that the current IME may not work well or even crash
	 depending on how the IME is implemented.

Bug: 111364446
Test: manual, use ActivityView & launch Messages in VirtualDisplay,
      tap search icon to see if soft input keyboard shown &
      app window size is adjusted by soft input.
Change-Id: I8da315936caebdc8b2c16cff4e24192c06743251