This removes the need for blocking queued connections and runAsync(),
reducing the risk of deadlocks and eliminating unguarded concurrent
access to various members of AndroidRunner. No mutex locking is
necessary anymore as all communication between the two threads is
either done on initialization, before the worker thread starts, or
via queued signals.

Change-Id: Icc2fcc2c0ce73d1c226bc4740413e57490d1cbc6
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>