Tracks whether an injected MotionEvent came from an accessibility tool.

This property can be checked by the View to allow sensitive views
to ignore gestures injected by non-tool accessibility services.
Sensitive views should continue responding to gestures injected
by Accessibility Tools.

Note: The files in this change do not reference the new flag, but this
change is a no-op if the flag is not enabled. See other change in this
topic.

Bug: 284180538
Flag: android.view.accessibility.prevent_a11y_nontool_from_injecting_into_sensitive_views
Test: atest InputDispatcher_test.cpp
Test: See other change in topic for tests using this property
Change-Id: I40ba79852045aaefe84f7ab87d5e08c42509f1e7