PIP: Disable hover show/hide menu if accessibility service is on.

With accessibility services on (e.g. Talkback), some MotionEvents get
transformed into HoverEvents. Notably in the case of TalkBack, tapping
on PIP will generate a pair of Hover enter/exit event, which then causes
the menu to immediately show/hide, and the user is unable to do
anything.

We will disable the hover behavior for Accessibility services, and allow
TalkBack users and such to open the menu via other menus (just tapping
it twice so it shows menu similiar to a regular user flow).

Bug: 152588263
Test: Enable talkback, enter PIP, tap once and then again - menu shows
Change-Id: I28c8faa0032bc2c7b8fa1ef5a9efde94a590293e