Use __call__ install of eval

[faymanns]

Replacing .eval with __call__() would make the API cleaner.
This applies to basis functions as well as splines.

Examples:
Instead of basis_function.eval(t, derivative=1) one could call basis_function(t, derivative=1) directly.
The same applies to splines: spline.eval(t) could be replaced by spline(t).

[faymanns]

Before the release of v1 a deprecation warning should be add to .eval.

[faymanns]

• When we remove .eval we should also stop ignoring A003 (shadowing of a Python builtin) in the ruff configuration.