Fix various GHA workflow bugs

[gregorydlogan]

This PR does a number of things:

• Fix spelling issue with 1af3f28
• Handling the case where there are no changes when removing a test instance. This doens't happen much, but it's super annoying to get spam when you're working on a bunch of things. f79d13c
• Renaming workflow to match both its filename, and what it's doing with 78c77e2
• Checking correct thing. We care that the repo executing the workflow is within OC, not that the originating repo is this one... This means that PR deploys should now work again. Fixed with 17275f1
• Reworks the workflow names. This is mainly cosmetic, but if you look at the full list in the Actions pane it's messy/annoying without 5bb2253
• Adds a check from the editor so that we refuse modifications to the non-en_US translation files with f444ba0. I'm 99% sure the path is right here, but we should check once this is merged - the syntax for this is unfamiliar to me.

This PR also includes #1464, so maybe review that one first.

[github-actions]

Use docker or podman to test this pull request locally.

Run test server using develop.opencast.org as backend:

podman run --rm -it -p 127.0.0.1:3000:3000 ghcr.io/opencast/opencast-admin-interface:pr-1466

Specify a different backend like stable.opencast.org:

podman run --rm -it -p 127.0.0.1:3000:3000 -e PROXY_TARGET=https://stable.opencast.org ghcr.io/opencast/opencast-admin-interface:pr-1466

It may take a few seconds for the interface to spin up.
It will then be available at http://127.0.0.1:3000.
For more options you can pass on to the proxy, take a look at the README.md.

[github-actions]

This pull request has conflicts ☹
Please resolve those so we can review the pull request.
Thanks.