More ruff and warning cleanup

[steinmn]

Bringing the number of ruff errors down below 50.

Part of #258

[sveinse]

@steinmn Do we want this in place before the pending 0.8.6 release?

[steinmn]

@steinmn Do we want this in place before the pending 0.8.6 release?

I don't think so. It's a lot of small changes which (hopefully) only impacts code quality stuff, so probably better to just get a stable version out and then have some more time to discuss all the points above.