Move repo to use "uv" tool

[benhoyt]

We should switch canonical/operator to use uv.

We could do this and go with uv+tox if it's easy, but it's probably best to wait till uv has its own task runner, which is on the Astral roadmap - see 9 Jan 2025 update.

Done as part of #1804:

• [x] set up the workspace
• [x] include ops, ./tracing and ./testing into the workspace
• [x] set up dependency groups
• [x] use dep groups in tox.ini instead of list of deps
• [x] update github actions
• [x] update readthedocs (server) config
• [ ] update README and HACKING

To do later:

• [ ] #1810
• [ ] #1811
• [ ] #1812
• [ ] #1813
• [ ] #1814
• [ ] #1815

[dimaqq]

Building docs: https://docs.readthedocs.com/platform/stable/build-customization.html#install-dependencies-with-uv

[dimaqq]

Blocked by https://github.com/tox-dev/tox-uv/issues/209 until we drop Python3.8 support.

[dimaqq]

wip: https://github.com/dimaqq/operator/pull/61