Update code coverage config

[vexx32]

PR Summary

Attempt to manually configure tests for Pester v5 and add code coverage that should (hopefully) work correctly.

Context

The automatic test coverage generation that -CI enables is not reading in our function files since we don't store function files alongside test files. Hopefully a more specific manual configuration should do the trick.

Changes

• Replace -CI switch with manually configured -Configuration settings.

Checklist

• Pull Request has a meaningful title.
• Summarised changes.
• Pull Request is ready to merge & is not WIP.
• Added tests / only testable interactively.
  • Make sure you add a new test if old tests do not effectively test the code changed.
• Added documentation / opened issue to track adding documentation at a later date.