API change for bridge.Transform.from_points

[bjlittle]

📰 Custom Issue

Align the use of the zlevels kwargs for geovista.bridge.Transform.from_points with the rest of the Transform API i.e., drop support for this being an array of values.

Support optional zs instead. See the point cloud use case.

This change will underpin follow-on work to the Transform API such that it supports volumes rather than surfaces, see #15.

Note, also impacts geovista.common.to_cartesian.

[welcome]

📢 Nice one! Your first issue! Thanks for telling us how to improve geovista 📢