LSI Correlator: Explore Decoupling from PCASpy

As a: Developer

I would like to explore how to decouple the LSI Correlator from [PCASpy](https://pcaspy.readthedocs.io/en/latest/) to clean up the codebase and allow for the creation of more tests to improve code coverage. Research should include creating a UML class diagram to display ideal architecture to move too and the creation of relevant issues to decouple from PCASpy.

### Acceptance Criteria
_What is the acceptance criteria?_
- [ ] UML diagram created and placed in [wiki](https://github.com/ISISComputingGroup/ibex_developers_manual/wiki/LSi-Correlator) to display ideal new structure for codebase when decoupled from PCASpy.
- [ ] New issues are created to begin decoupling from PCASpy including relevant sections of UML class diagram created for context.

### Extra Information
- Dev manual link: https://github.com/ISISComputingGroup/ibex_developers_manual/wiki/LSi-Correlator
- Support repository: https://github.com/ISISComputingGroup/EPICS-LSICorrelator
- IOC directory: https://github.com/ISISComputingGroup/EPICS-ioc/tree/master/LSICORR
- PCASPy: https://pcaspy.readthedocs.io/en/latest/

_Why it is needed?_
To reduce coupling with PCASpy and increase code coverage.

Justification to decouple is that currently, a reasonable amount of functionality is written inside `correlator_pcaspy.py` which is currently untested.
Tight coupling to third party code is also bad practice generally speaking.

_Where required files/links are_
https://github.com/ISISComputingGroup/EPICS-LSICorrelator/blob/master/correlator_pcaspy.py