Eurotherm (modbus): find solution to scaling factors [Timebox: 4.5 days, 0.5 to review]

## Where?

In https://github.com/ISISComputingGroup/IBEX/issues/4240 basic communications with eurotherms using modbus were implemented. However, it currently needs a large number of scaling factors to be set up for each eurotherm crate - these scaling factors are very error-prone.

Eurotherms theoretically have an IEEE modbus region which provides access to full-resolution floating-point parameters, which should not be subject to these scaling problems. However we have currently been unable to read this IEEE modbus region on our office eurotherms - either 2000 or 3000 series.

This ticket is to investigate this IEEE region in more detail:
- Try updating firmware on a eurotherm, see if this helps
- See if we can extract the scaling factors we need from the eurotherm itself - analysis in ticket 4240 did not find anything suitable, but re-check manual.

## How?

This is a sub-ticket of https://github.com/ISISComputingGroup/IBEX/issues/4240

## Acceptance criteria
- [ ] We can communicate reliably with eurotherms on modbus, without needing to input large numbers of scaling factors in an error-

## How to Test
_verbose instructions for reviewer to test changes
(**Add before making a PR**)_