GeoJsonPrimitive: Fix tessellation at poles and antimeridian

### What happened?

GeoJsonPrimitive polygon triangulation fails near the north pole and for polygons that cross the antimeridian. I haven't debugged further yet but I expect that we'll need to split polygons crossing the antimeridian.

Also see iTwin.js examples on greedy tessellation between line strings:
https://www.itwinjs.org/learning/geometry/triangulation/

### Reproduction steps

See:

- [countries.json](https://github.com/user-attachments/files/28318836/countries.json)
- https://github.com/CesiumGS/cesium/pull/13505#issuecomment-4550205669

### Sandcastle example

_No response_

### Environment

n/a

### AI acknowledgment

- [ ] I used AI to generate this issue report.
- [ ] (If the above is checked) I have reviewed the AI-generated content before submitting.

Start by reproducing the triangulation failure with countries.json and compare the behavior with the iTwin.js greedy tessellation example. Trace the GeoJsonPrimitive polygon triangulation entry point, then verify that polygons near the north pole and crossing the antimeridian triangulate correctly without the reported failures.

Written by the indexing model from the issue text.