Box3D predicates: ST_3DBoxIntersects and ST_3DBoxContains

[jiayuasu]

Follow-up to the Box3D Phase 1 epic (#2973). Adds the two Box3D-on-Box3D spatial predicates.

Scope

• ST_3DBoxIntersects(box3d, box3d) -> boolean — closed-interval intersection on all three axes. Matches PostGIS's &&& 3D overlap operator.
• ST_3DBoxContains(box3d, box3d) -> boolean — closed-interval containment on all three axes. Matches PostGIS's ~~ on box3d.

Semantics

• Closed-interval — edge/face/corner contact counts as intersecting and contained. Parallel to the Box2D contract on ST_BoxIntersects / ST_BoxContains.
• Inverted bounds (xmin > xmax, ymin > ymax, zmin > zmax) are rejected with IllegalArgumentException. Z does not wraparound, so we do not carry forward Box2D's "reserved for future antimeridian wraparound" exception.
• NULL input → NULL result (no in-band empty marker).

Out of scope

• Spatial join planner integration (separate follow-up — see EPIC).
• Filter pushdown for Box3D predicates against Box3D columns.
• ST_3DDWithin distance predicate (separate follow-up).