fix: rename internal plugin repository functions

[jthegedus]

Summary

Use plugin in the function name for functions that reference the plugin repository.

I was making these changes in #1437 and thought they could be pulled out separately for easier review.

Other Information

I am torn about the impact on semver here (fix or chore). On the one hand, code is being changed that users would execute, so this code should be released under a new version, a fix. Whereas the external API is not being changed so it could probably be a chore with the change going out with the next release (any subsequent fix or feat). 🤷

Historically I have been encouraging any change to code that effects the user to go under fix, even if just code style changes, so will stick to that here. But this is certainly open to discussion should anyone care.