Always reload AccessibiiltyInputFilter on user switch

Makes AccessibiilityInputFilter aware of current user ID, and pasess the
user ID to event stream filters that have per-user parameters:
- AutoclickController -> for per-user autoclick delay
- ScreenMagnifier -> for magnification scale

While doing this, make AccessibilityInputFilter.disableFeatures private,
and replace usage in AccessibilityManagerService with
setUserAndEnabledFeatures with feature flags set to 0:
Using disableFatures directly leaves input filter in inconsistent state
where internal mEnabledFeatures flags don't match real state of enabled
features.

BUG=23113412
BUG=24265227

Change-Id: Ib295f4c08de1a3743e55714459844b6d80787637