Add GeoPoint shape type for geo_shape query

[m15flores]

Closes elastic/elasticsearch-java#501

Adds a GeoPoint type in _types/Geo.ts, following the same shape as the existing GeoLine, and references it from GeoShapeFieldQuery.shape as GeoShape | GeoPoint.

Tried adding GeoPoint standalone first (like GeoLine), but it gets dropped as a dangling type since nothing points to it (GeoLine only survives through the aggregation reference). Referencing GeoPoint from shape fixes that without changing GeoShape itself, so this isn't a breaking change: raw JSON shapes still work exactly as before, GeoPoint is just an additional typed option.

Tested against a live 8.15.0 cluster: querying a geo_shape field with {"type": "point", "coordinates": [...]} as the shape returns the expected results.

[l-trotta]

Thanks @m15flores! Couple things: while this is not breaking for the java client, it could be for other clients that don't override to JsonData, so I'll have to check before merging; also, could you add a comment about this being a hackfix?

[m15flores]

Hey! Added the hackfix comment. Let me know if there's anything I can help verify for the other clients.