AccessibilityBridge installs various listeners for Android events
that invoke Flutter engine APIs. These listeners are removed in
AccessibilityBridge.release. However, in some environments there may
be deferred calls to the listener that will still execute even after
the listener has been removed. This change sets a flag during release
and ignores any listener invocations that happen after the flag is set.
See https://github.com/flutter/flutter/issues/63555 and
https://github.com/flutter/engine/pull/17311
