EPICS Base repo structure: Move from imports to forks

## User story
As a developer, I would like to for the base EPICS repos into our system now that they exist so that updating from them, or offering solutions to them, is simpler and we can treat them in the same way as other github hosted items in our software base.

## Explanation
Initially simply forking things wasn't an option, it is now, and updating this part of our system, which had acquired technical debt, could make future updates of the code/system easier.

# Acceptance Criteria
- [ ] Generate a list of repos which can be updated in this way in a comment on this ticket
- [ ] Create tickets to swap each of them to a fork and update the rest of the system to use that instead, running and adding tests as appropriate (there should be a ticket per repo in the list, unless some obvious grouping comes up, in which case that should be detailed in comments in this ticket)

# How to Review
- [ ] There is a list that looks suitable, and tickets created as per any notes here for the migration to forks