Give the Cesium renderer a quality port

The Cesium quality port supports pixel ratio, multisampling, shadows,
3D tile and terrain detail and the target frame rate, each applied when
first set and nothing changed before. Detail scales each tileset's and
the globe's own screen-space error and gives it back at full detail;
while tile detail is lowered, tilesets added later follow it. Frame
signals carry each drawn tick's CPU time, size, loop mode and holds.
The application and conformance renderers have the port, and the
conformance page runs the quality checks against Cesium.

scripts/package-boundaries.json

@@ -2760,6 +2760,7 @@
       "src/render/creditMarkup.js",
       "src/render/rendererOf.js",
       "src/render/cesium/ports.js",
+      "src/render/cesium/quality.js",
       "src/render/cesium/credits.js",
       "src/render/cesium/effects.js",
       "src/render/cesium/common.js",