[MNT] Replace `tj-actions/changed-files`

[MatthewMiddlehurst]

Describe the issue

https://www.stepsecurity.io/blog/harden-runner-detection-tj-actions-changed-files-action-is-compromised

The repo owners did a bit of an oopsie and now the action no longer exists. This is mainly used in our pre-commit action on PRs to only look at changed files.

EDIT: The repo is available again, but it would still be good to find a replacement.

Suggest a potential alternative/fix

Find/write and alternative. This does not have to be an action, you can just find the changed files manually.

Additional context

There are some security implications for this with using tags in GitHub actions, but I'm not sure replacing every action import with a SHA is a trouble free solution. I don't see anything leaked on our end.

[Sharathchenna]

Hey, @MatthewMiddlehurst, can I try to work on this?

[MatthewMiddlehurst]

Please only assign yourself to this issue if you have a solution in mind and have a PR ready.

[Kaustbh]

Can't we use alternative actions available?

[MatthewMiddlehurst]

Part of solving this issue is finding those, I have not looked for alternatives. This is less important now that our CI works again.