Update to copier template 2.3.0

[coretl]

Probably unreviewable PR, that adopts the latest copier, bringing:

• autosummary docs that look like scanspec's
• bugbear and pyupgrade (fixes Add Bugbear and pyupgrade linters to ruff #488)
• pyright checking, with errors mostly fixed and sometimes ignored

[evalott100]

With a PR this big I defer to your judgement 😛

The only places which raise an eyebrow somewhat are the slight changes which do actually change functionality (e.g kwargs to args).

I think it's best to merge and clean things up during testing.

[evalott100]

There was one method somewhere I found yesterday where a kwarg was converted into an arg. I didn't raise it as a problem... It probably isn't.