Support websocket connection in scripting interface

[tpoliaw]

The BlueapiClient support for running plans via websockets is limited to the new run_blocking method. The scripting interface (eg bc.plans.count(...)) still uses the existing stomp connection.

While the websocket connection is still experimental, there should be some way of opting in to use it for the scripting as well. Potentially an option on the client? on the plan cache?

# option on the client
bc.use_websockets = True

# option on the plan cache
bc.plans._websockets = True

Is there a simpler/more convenient approach?