SedonaFlink: add geography constructor functions (ST_Geog*)

[jiayuasu]

Part of #3054.

Scope

Expose the geography constructor/conversion functions in SedonaFlink, registering them so they are callable from the Flink Table API / SQL — reaching parity with the 9 functions Spark exposes.

Depends on #3058 (GeographyTypeSerializer), now merged.

Functions

• ST_GeogFromWKT (wkt, [srid])
• ST_GeogFromText (wkt, [srid])
• ST_GeogFromEWKT (ewkt)
• ST_GeogCollFromText (wkt, [srid])
• ST_GeogFromWKB (wkb, [srid])
• ST_GeogFromEWKB (wkb)
• ST_GeogFromGeoHash (geohash, [precision])
• ST_GeogToGeometry (geography) → geometry
• ST_GeomToGeography (geometry) → geography

Tasks

• Add ScalarFunction wrappers in flink/src/main/java/org/apache/sedona/flink/expressions/GeographyConstructors.java, each delegating to org.apache.sedona.common.geography.Constructors with @DataTypeHint(value = "RAW", rawSerializer = GeographyTypeSerializer.class, bridgedTo = Geography.class), matching Spark's optional-argument defaults (srid 0, geohash precision null).
• Register all 9 in flink/src/main/java/org/apache/sedona/flink/Catalog.java.
• Add tests round-tripping each function through the Flink type system (GeographyConstructorTest).

Docs are tracked separately as the next sub-task.