switch to scikit-build-core to avoid setup.py

[nathanhhughes]

Got around to reworking the packaging to (eventually) work with ros2 with the current package layout. I'm not fully convinced that this works on 20.04, so might be worth starting the ros2 branch off of this

[nathanhhughes]

Update:

• It installs on 20.04 (after upgrading pip in the virtual environment)
• Moving pyproject.toml inadvertently broke ruff (it was using it for settings) in a way that made it hard to restore the isort black profile. I opted for something sane-ish for ruff's import sorting directly, but we can change it if we want
• I added an optional dependency target for installing (some) of the required SALAD + lightglue deps
• Instructions are up to date
• I added COLCON_IGNORE to all the packages. This should stay for ouroboros, but can be dropped once we transition the ros packages Nevermind, catkin also ignores COLCON_IGNORE

Might be worth merging into main after all, I think this doesn't break anything and should be a good ros2 jumping off point

[yunzc]

lgtm!