Modernise pyproject

[Monarda]

The pyproject.toml is a little outdated and needs to be modernised to recent recommendations.

Update package versions to latest and validate.
Switch tests and dist from optional-dependencies to dependency-groups (PEP 735).
Possibly other changes!

[Monarda]

I've enabled the following ruff additional options in pyproject.toml:

  "B",     # flake8-bugbear; https://docs.astral.sh/ruff/rules/#flake8-bugbear-b
  "ASYNC", # flake8-async; https://docs.astral.sh/ruff/rules/#flake8-async-async
  "SIM",   # flake8-simplify; https://docs.astral.sh/ruff/rules/#flake8-simplify-sim

They have triggered lots of small one or two line changes throughout the code base.