Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes into CHANGELOG.md):

Fixed GeoParquet causing client protocol errors.

1. getNamesAndRecursivelyNullableTypes took type Point, aka Tuple(Float64, Float64), turned it into Tuple(Nullable(Float64), Nullable(Float64)), and named the resulting type "Point" again (!).
2. When server sends blocks with such columns, it sends data type name "Point" and column serialized as nullable (Tuple(Nullable(Float64), Nullable(Float64))).
3. Client then receives type name "Point", calls DataTypeFactory::get("Point") to learn that "Point" means Tuple(Float64, Float64), and proceeds to deserialize column data as non-nullable. So it outputs garbage data and some error like "Unknown packet 0 from server".

This PR removes the code that reassigns custom name to a different type, and adds code to avoid making parts of named types nullable. So getNamesAndRecursivelyNullableTypes leaves Point unchanged, non-nullable.

(Same for the other geo types: LineString, Polygon, MultiLineString, MultiPolygon.)