[Media] Reject seek bar scrubbing if too vertical.

If a drag gesture begins on the seek bar and that drag gesture ends up
being more vertical than horizontal, don't commit the result of the
scrubbing when the drag gesture ends.

As it turns out, there's no support for this in the Slider composable
from the Material library. It just reports onValueChangeFinished
regardless of how vertical the drag was; it doesn't even have a
mechanism by which to observe or receive the actual delta.

Therefore, I went around it. I used .pointerInput which is the low-level
user input API in Compose to just watch for all gestures on the Slider.
Then, I collected and reported the drag delta to the view-model so it
has the information it needs to make its own decision when it handles the
onValueChangeFinished.

Bug: 397989775
Test: manually verified in the Compose Gallery app - starting a drag in
the bounds of the seek bar, dragging too far up or down, and releasing
reverts the position back to where it first was. Also verified that
doing the same but going more horizontally than vertically works
correctly.
Flag: EXEMPT - code not yet used in production code.

Change-Id: I5998cc8dd161769036f7e3a654394df24c9f9b2d