Add columnar icon sets drawn by an instanced Cesium primitive

Icon rows live in typed-array columns: one packed motion segment (hold,
lerp or arc, with a course glide), style, colour and pick ids per row.
The primitive draws every row in one instanced call, dead-reckons in the
vertex shader, matches the billboard treatment the fleet layers use, and
picks and drill-picks like a billboard. Cyber sonar covers icon sets.

scripts/package-boundaries.json

@@ -2259,6 +2259,10 @@
       "src/hudLayoutPolicy.js",
       "src/ui/radioPanelPlacement.js",
       "src/cyberSonarGpu.js",
+      "src/data/iconSetPrimitive.js",
+      "src/data/iconSet.js",
+      "src/data/iconSegment.js",
+      "src/data/iconAtlas.js",
       "src/scenes/nepalEvidencePack.js",
       "src/data/approxDistance.js",
       "src/data/bhoteKoshiEvent.js",