ENGINX: Output power ramp rate issues on Eurotherm

# Issue Description

**Aim to not delete parts of the template.**

~~~
As an instrument scientist, I find some issues with the Engin-X Eurotherm OPI. Specifically:
1) The rate is in power% per second, not % per minute like the block/PV displayed units come up as.
2) The rate setpoint readback value (and presumably the actual rate) are quantised to 0.01 increments, which is not fine enough given this is power% per second.
3) If a rate of 0.005 is entered, the displayed setpoint readback rounds up to 0.01. However the power changes are then actually instantaneous, with no rate applied. This is normal behaviour for when a rate of zero is entered. Could the logic for checking for a zero entered rate be rounding the 0.005 value down to zero and hence disabling the power ramping, even though the setpoint readback is rounding this value upwards to 0.01?

~~~

### How & Where?
- Reported by Joe Kellher from ENGINX
- The issues are related to the power ramp rate in the Engin-X Eurotherm OPI

### Reproducible (Yes/No)?
Will update after further discussions with ENGINX.

### Additional Information
Not applicable

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# Acceptance Criteria
- Issues are fixed in the OPI
- The expected values are shown in the Ibex GUI

# How to Review

_{**To the reviewer: Make sure to [update submodules](https://isiscomputinggroup.github.io/ibex_developers_manual/processes/git_and_github/Git-workflow.html)!**}