Clear relative axes in resampled events

When a resampled event is synthesized, PointerCoords instance is copied
from the last sample, and updates X and Y coordinates.
This copies all axes from the old pointer, but there are "relative"
axes, such as AXIS_RELATIVE_X, AXIS_RELATIVE_Y, AXIS_GESTURE_X_OFFSET,
etc. These values are relative from the last "real" sample, not from the
resampled sample.

With this change, these axes are populated with zero when an event is
resampled. This helps consumers of these values to correctly track
and accumulate value changes.

Bug: 423433478
Test: TouchResamplingTest, ResamplerTest
Flag: com.android.input.flags.clear_relative_axes_in_resampled_coords
Change-Id: I7090e4bbfeeedf1bd4dfd2b7f7862a1c4f45df18