Draft: Resolve "BEC Figure RPC tests fix"

This MR proposes a fix for the issue @wyzula_j showed me yesterday

2 main problems:

• the major one, was that during the wait loop signals/slots could not execute
• the minor one, BECDispatcher in server was the same instance as in client ; in addition BECClient was a singleton too

the test I added in this MR is just to demonstrate the problem and the solution, it has to be replaced by the real test