PLH250DCPS power supply

### Goals
Acceptance criteria : What journeys should the user be able to complete to consider your feature done
Be as specific as you can, check them off once they work. Add more if you find more requirements during development. Issue should only be considered done after all of them are checked
- [ ] User should be able to launch PLH250DCPS server via `sm_bluesky start` cli command
- [ ] Document the new routine startup procedure for the beamline team
- [ ] Server automatically reconnects if the physical power supply is power-cycled.
- [ ] Optional: Remove the need for user to look up IP manually.

### Tasks
base on the goals, deduce the tasks required. check them off once they're done
- [ ] Create PLH250DCPS base on AbstractInstrumentServer.
- [ ] Add cli to start the server.
- [ ] Update gda scanable.
- [ ] Look into the possibility of getting the IP of the connected instrument via its MAC address.
### Related Resources
Possible options for getting the IP:
[Scapy](https://scapy.net/)
[get-mac](https://pypi.org/project/get-mac/)

Start by locating AbstractInstrumentServer implementations and the entry point for the `sm_bluesky start` CLI, then inspect how the GDA scanable is updated. Define the PLH250DCPS server's startup and power-cycle reconnect behavior, document the beamline startup procedure, and verify the CLI launch and reconnection criteria; investigate Scapy or get-mac only if IP discovery remains in scope.

Written by the indexing model from the issue text.