Skip moving PiP for IME/shelf change if user is dragging.

Tapping on the PiP will already make isUserInteracting equal to true.
However, user might have simply tapped it to open the menu.
Defer the movement only if user is actively dragging PiP (aka changing the position of PiP while using another touch point to e.g. open IME).

This also will make PiP move above IME anyways, when user finishes the
drag.

Bug: 255689034
Test: open PiP, tap it to show PiP menu, open IME, pip moves away
Test: open PiP, while dragging open IME with another finger, pip stays
Change-Id: If5830ed783cf969d4eba8a91f235e008a6e13680