Add presentTime to FrameInfo

Present time is available to apps, but is not currently stored inside
FrameInfo. In this CL, we add a location for storing the present time inside
FrameInfo.

Currently, the metrics reporter is triggered after the buffer is sent to
SurfaceFlinger. That means, metrics for anything that happens after gpu
draw completes are currently not available.

In a future CL, we will populate the 'presentTime' field.

In a future CL, we will register a metrics observer inside ViewRootImpl
in order to send this data to InputDispatcher. This will enable
end-to-end touch latency metrics collection.

Bug: 169866723
Test: printed present time inside FrameTimeline.cpp (surfaceflinger
side) and compared to the values printed inside a metrics observer
registered in ViewRootImpl (not done in this CL)
Test: atest ViewFrameInfoTest

Change-Id: I7d0f8c5d7b5a2572abdc4e107123e8938a36f582