Remove observer toggles

[manishmeganathan]

• Reimplement the concept of observer toggles. Use a pointer to a field in the MeshOrchestrator struct instead of a variable inside the runtime, similar toSimulatorOn. Let's call it ObserverationOn.
• Use the same new field to also lock the Observation method of the server, such that only one mesh observer can connect to the mesh log stream at any given point in time. Treat it essentially as a synchronisation lock for the observation log stream.