Give the Cesium renderer the contract's globe port

The globe port sets the base (photoreal tiles, terrain, imagery), shows
or hides the globe, and adds imagery layers: XYZ, WMTS, ArcGIS, world,
single-image and canvas sources, with admission, fetch and transform
hooks, a request budget and tile errors. Each layer drapes where its
drapeOn says: on the globe, or on the drawn base tileset, which is the
port's own photoreal tileset or one the map stack marks as its base,
followed every frame so a base switched outside the port moves the
layers. Port layers keep their order above other layers in each
collection. The sky reads the scene and writes through to it, and the
port reports settling and load progress.

The application renderer and the conformance renderer both have it, so
the application renderer now has every member of the contract. A viewer
with no renderer bound gets a globe port through findGlobe. The Cesium
conformance run checks imagery order, the split and the image-hook gate.

scripts/package-boundaries.json

@@ -2781,6 +2781,7 @@
       "src/render/creditMarkup.js",
       "src/render/rendererOf.js",
       "src/render/cesium/ports.js",
+      "src/render/cesium/globe.js",
       "src/render/cesium/quality.js",
       "src/render/cesium/credits.js",
       "src/render/cesium/effects.js",
@@ -3184,6 +3185,7 @@
       "src/maps/imageryComparison.js",
       "src/maps/credits.js",
       "src/maps/defaultSources.js",
+      "src/render/cesium/imagery.js",
       "src/maps/google3d.js",
       "src/maps/imagery.js",
       "src/maps/registry.js",