[GH-3475] Correct the GeoStats Python docstrings

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• Yes, and the PR name follows the format [GH-XXX] my subject. Closes GeoStats Python docstrings are missing or wrong #3475

What changes were proposed in this PR?

Docstring-only changes in python/sedona/spark/stats:

• Moran, Moran.get_global and MoranResult: new docstrings. They describe the input get_global needs (an id column, a numeric value column, and a column named weights whose neighbors carry the id and value columns, for example from add_distance_band_column with saved_attributes) and the three result fields.
• dbscan: include_outliers defaults to True.
• g_local: point to sedona.spark.stats.weighting.add_distance_band_column, say that include_self=True puts the focal observation in its neighbors for Gi*, and name the added columns EG and VG as the Scala code does.
• weighting: the new column is named by result_name ('weights' by default), not 'cluster'. add_weighted_distance_band_column weights are dist^alpha and alpha is required. Only weighted distances with a negative alpha give infinite weights, so add_binary_distance_band_column no longer mentions them.
• A blank line before Returns: in add_distance_band_column and g_local, so docstring parsers such as griffe read it as a section.

How was this patch tested?

• Checked each statement against the Scala implementations (DBSCAN, GetisOrd, Weighting, Moran).
• Parsed the module with griffe: every function and class now has its parameters and returns documented, with no section warnings.
• pre-commit run on the changed files passes, and the files compile.

Did this PR include necessary documentation updates?

• Yes, this PR updates the Python docstrings.