Add generics to geom.util extractors (fixes #1113)

[micycle1]

This PR addresses #1113 by adding type parameter declarations to the geom.util extractor utilities, reducing raw List/Collection usage and the need for casts in user code.

Changes:

• Extractor methods now return typed collections (List<Polygon>, List<LineString>, List<Point>)
• Added Collection<? super T> overloads so you can collect into either Collection<T> or Collection<Geometry>
• Consolidated extraction logic into GeometryExtracter (new extractByClass(...) helpers) to avoid duplication
• Kept extracters implementing GeometryFilter for Geometry#apply(...) compatibility

Compatibility:
Mostly backwards compatible. Note that due to Java generics, returned values like List<LineString> cannot be assigned to List<Geometry>:

List<Geometry> rings = LinearComponentExtracter.getLines(geom); // won't compile
List<? extends Geometry> rings = LinearComponentExtracter.getLines(geom); // works
List<LineString> rings = LinearComponentExtracter.getLines(geom); // works

This PR only touches geom.util. These changes involve more design decisions than straightforward "add generics" fixes (like getNodedSubstrings), so broader changes are left for a future PR.

[micycle1]

I've kept untyped methods like List extract(Geometry geom, Class clz, List list) and such in GeometryExtracter, but this could be a time to remove them completely.