Switch from Poetry to uv?

[tompollard]

@Rutvikrj26 see the issue raised at: #2686. Builds were failing with Poetry v2, so we have pinned v1 in the test for now.

Instead of addressing the Poetry issue directly, I wondered whether it might be a good time to reconsider Poetry vs uv?

A lot of people seem to like uv, and Poetry seems to have declined in popularity (anecdotally, I don't have any good evidence for this!).

[Rutvikrj26]

@tompollard I like uv too - all of my other projects use uv - This is a good idea to switch to uv - I'll add it to my backlog.