The QAndroidJniEnvironment class does not detach when it goes out of
scope. Detaching will only happen if explicitly done, or if the thread
we attached on dies.

Fixes: QTBUG-73570
Change-Id: Iac749c7f3bf8fcee99f70c06123eb3c88315e261
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>