Makes the multi-touch prevention only works for editable TextView.

The original logic of preventing the multi-touch issue for the edtiable
text view was introduced by ag/10930920.
Turns out the non-editable text views are affected.

The root cause of the issue is that:
 - the ACTION_DOWN/ACTION_UP events, as well as ACTION_PONITER_DOWN /
   ACTION_POINTER_UP, could be generated by different fingers,
 - and View#onTouchEvent() gets muted when isFromPrimePointer() == false,
 - so that no gesture is generated, e.g. click, long press, etc.

Note that View#onTouchEvent() is necessary to be muted to prevent long press
on text or scrolling while dragging the insertion handle view.

Bug: 169288151
Change-Id: Ia763e94be727ad23bb13839f146293f1579d03ec