Remove window obscurement information from ACTION_OUTSIDE events.

If ACTION_OUTSIDE_EVENTS contain information about whether the touch is
obscured, then a pattern of invisible, untouchable, unfocusable
SYSTEM_ALERT_WINDOWS can be placed across the screen to determine
approximate locations of touch events without the user knowing.

Bug: 31097064
Test: cts-tradefed run commandAndExit cts-dev -m CtsSecurityTestCases -t android.security.cts.MotionEventTest
Change-Id: Iea968ce23e018acf95116896a1ba4c065885b760