Move launcher process into a separate thread.
Implement blocking API by using wait condition
on the caller's side. Replay all collected
signals from the launcher's thread when leaving
waitingFor* state. In case we were not waiting
for anything deliver the signals asynchronously
from launcher's thread to the caller's thread.
Change-Id: Id44fe5f7ceaac407004984a1dfb6ea65f197d297
Reviewed-by: hjk <hjk@qt.io>