Fix keyboard focus in VR

Consider this VirtualDisplay (VD) scenario:
HostActivity creates a VD which holds SettingsActivity. When EditText
on SettingsActivity is tapped, it gains focus.
On eventual taps, it loses focus i.e. the Window in VD loses focus and
the host activity in primary display gets the focus instead. This
happens because WM's TaskTapPointerEventListener.onPointerEvent()
is called on the default display only.

Root cause:
1. Tap detector isn't registered for non-default display.
2. Tap detector has no info on which displayId touch was received.
3. InputFlinger doesn't deliver InputMonitor events for
non-default displays (fixed in a separate CL)

Fixing above results in onPointerEvent(MotionEvent) to deliver the
Touch events successfully to VD. We restrict these changes to physical
multi-displays and VR VirtualDisplays (which uses virtual touch device).
[VrManagerService calls WMInternal.setVr2dDisplayId(int)]

In future, displayId should be part of InputEvent. Bug: 64258305

Bug: 62033391
Test: bit FrameworksServicesTests:com.android.server.wm.DisplayContentTests
Change-Id: I3626f4de5aa9bcf905da9abd39f3ab1baefc4c48