Chore: Use ArtemisImageProvider everywhere + Update to coil3

[FelberMartin]

Description

While working on #111 I introduced the new ArtemisImageProvider class which should be used to load all image related resources. I discovered that using the ArtemisImageProvider for loading course icons works, but there is a problem with the PlayStoreScreenshots. In order to intercept the ImageRequests the recommended way is to use a AsyncImagePreviewHandler which comes with coil3.

Updating the dependency and using the new ArtemisImageProvider everywhere seemed to blow up the PR, so lets tackle this separately.

Next steps

• Update coil to coil3 https://coil-kt.github.io/coil/upgrading_to_coil3/
• Use the ArtemisImageProvider for loading course and server icons, and creating the MarkdownImageLoader introduced in Communication: Fix link rendering for attachments and show uploaded images in chat #109