Fix Tupan test failures with numpy ≥2.4.0 (fixes #1256)

[elkogerville]

Fixes #1256

Problem:
Tupan tests fail with numpy ≥2.4.0 due to incompatible dtype handling in commit_particles. The method was assigning 0-dimensional np.ndarray objects to ParticleSystem attributes instead of scalars.

Solution: Refactored particle management to use amuse.datamodel.particle module.

• new_particle: Changed to instantiate Particle objects and accumulate them in a Particles object (instead of creating single-element ParticleSystem instances)
• commit_particles: Convert the accumulated Particles object to a ParticleSystem before passing to Tupan

Test Status:
All uncommented tests pass. Tests xtest04, xtest08, xtest10 remain commented because they test unimplemented features (stopping conditions, get_gravity_at_point).

Additional Changes:

• Removed redundant get_eta and set_eta from Tupan methods as they are already defined as parameters.
• Refactored TestTupan::test02 as it was testing parameters that do not exist.
• Removed Tupan being listed as a dependency of Tupan in the pyproject.toml