Implement I16 Offsets in Bluesky

I16 has a number of values ('Offsets') that they want persisted between GDA restarts, mostly to do with beamline alignment. They have to be able to modify these easily during operation and have the new value persisted. This is currently done using python's shelve functionality, with the values stored in {gda.var}/oldStyleShelveIO. They are required for the energy calculation

I think this could be done using the functionality described here https://blueskyproject.io/ophyd-async/main/how-to/store-and-retrieve.html, writing the persistent values to yaml. It might be best to have each as a separate readable (offsets are currently scannables), I think you would want only one file for all offsets though so some sort of manager would be required to handle that.

### Tasks
- [ ] Implement a replacement for this Offset functionality
- [ ] Add all offsets currently defined to configuration in bluesky (can be done as they are needed)