Move Changes action locally

[edmundmiller]

Attempting to move detect changes action to a local action in this repo.

#7007 (comment)

All good - complexity is bordering on too much now. It's a shame we can't redirect individual tests to specific hardware, you know...like a certain piece of software does very well.

This manages most of the issues well. @adamrtalbot

On the complexity, after we merge this one can we migrate the action to live in this repo? I think that structure works better for the mono-repo so these PRs aren't so complicated to test/hack on. @edmundmiller

[mashehu]

What is the reason for making detect-changes local?

[edmundmiller]

What is the reason for making detect-changes local?

I added some more context; sorry! I just wanted to get the ball rolling because @maxulysse asked about it in Slack.