Now that all code conforms with the new style, we can remove all
the tricky bits that compare errors from regular- and legacy
config or limit checks to changed lines from a git diff.
All that is left over the eslint CLI tool is the ability to output
results both as junit for gitlab and plain text for logs without
duplicating the linting, but that's well worth preserving.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2866>
The eslint jobs report their results as artifacts in junit format,
so that gitlab can present them in its UI.
However many people miss that, and unsuccessfully check the logs
instead.
Account for that by also printing the results to stdout.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2829>
This is unnecessary hard in shell when compared to a proper programming
language. It becomes even easier with a node-js script, as that gives us
access to the underlying ESLint module rather than just the CLI interface.
Besides that, node-js has the added benefit that we don't need to add
more dependencies to the CI image.
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1497
