feat: model_updater easy to get for more custom rerun use cases

[Ipuch]

@aceglia

import rerun as rr
import numpy as np
from pyorerun import ModelUpdater

q = np.zeros(10)
model = ModelUpdater.from_file("path/to/model.bioMod")

rr.init("my_thing", spawn=True)
rr.set_time_sequence(timeline="step", sequence=0)
model.to_rerun(q)
rr.log("anything", rr.Anything())

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