Add support for MultiPoint and Point in MAXAR_content_geojson

[lilleyse]

Adds support for MultiPoint and Point in GeoJsonLoader.

For background see the original PR where support for MAXAR_content_geojson was added: #10356

The diff makes the PR look more involved than it actually this. Basically there are two changes:

• Update the parsing code to read MultiPoint and Point and save the point coordinates in the feature
• Convert the points to a ModelComponents.Primitive

Local sandcastle

[cesium-concierge]

Thanks for the pull request @lilleyse!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.

[ptrgags]

@lilleyse looks good, I just noticed a few places that could use some minor refactoring

[lilleyse]

@ptrgags updated!

[ptrgags]

Looks good, thanks @lilleyse!