Write a tutorial on how to write a simulation for a stream device

Issue moved from tickit as it is more appropriate here.

To improve uptake of tickit more generally we should make it easy for a controls developer at DLS to make a new device from scratch. Currently the documentation is more geared towards core ticket developers, not device developers. We need to have both.

The tutorial should cover:

1. Given a simple stream device IOC
2. How to implement the adapter
3. How to connect your IOC to it
4. How to write system tests that prove your IOC

An example device:
https://gitlab.diamond.ac.uk/controls/support/bronkhorstflowbus/-/blob/master/bronkhorstFlowBusApp/Db/coriFlow.template