Add a property to access vector dimensionality

[adrn]

I thought it might be useful to add this shorthand.

[adrn]

This rule is deprecated: https://docs.astral.sh/ruff/rules/pytest-missing-fixture-name-underscore/

[nstarman]

I agree this would be a useful property!
Two notes:

1. Except for the ND classes this should be a class-level property.
2. is this too similar to ndim?

[adrn]

Except for the ND classes this should be a class-level property.

👍

is this too similar to ndim?

I thought about .dimensionality but that is too long. 🤷

[adrn]

Except for the ND classes this should be a class-level property.

Actually won't this end up creating a lot of copy-pasted code? It would need to go on the position, velocity, acceleration, and need the docstring to follow for 1D, 2D, 3D, 4D. Isn't it cleaner to just compute it automatically as in the current implementation?

[nstarman]

Isn't it cleaner to just compute it automatically as in the current implementation?

components is already a class-level property, so it shouldn't be much of a change.

@classproperty
@classmethod
def dims(cls) -> int: ...

And I think components is incorrectly (?) 1 for CartesianND because that's calculated as...

@classproperty
@classmethod
def components(cls) -> tuple[str, ...]:
    return tuple(f.name for f in fields(cls))

[nstarman]

I've had to add a private implementation of this ._dimensionality. I think there should be a public version, though! This PR can be rebased and modify the private version into something a bit more user-friendly. :)