Reimplement introspection using fastcs odin adapter

[GDYendell]

https://github.com/stfc-aeg/odin-fastcs/tree/client_set

@timcnicholls I think things are now in a good place to look at this in parallel with other ongoing developments. Do you have time to look into implementing the FastCS side of this? If not, would you be able to summarise the interface of fastcs adapter so that someone else could potentially pick this up?

For reference, currently we get the adapters list, then do a get at the root of each found adapter to get their parameter trees and create sub controllers for each one. This is done here.