refactor(credits): use the globe engine

Map credits (maps/credits.js) are shown through a credits capability
(engine.credits.addStatic) instead of the scene's credit display; the
shared map scene takes the engine's credits, so the Cesium engine's maps
and its credits part share one owner. Data credits (registerDataCredits,
registerDynamicCredit, show/hideOsmCredit) take the globe engine and keep
accepting a viewer from layers that still hold one; the scene registers
the data credits on its engine. The Cesium credits part reads
Viewer.creditDisplay, else the scene frame state display it aliases.

scripts/package-boundaries.json

@@ -1607,6 +1607,7 @@
       "./maps/defaults"
     ],
     "modules": [
+      "src/globe/cesium/credits.js",
       "src/maps/availability.js",
       "src/maps/catalog.js",
       "src/maps/controller.js",
@@ -3086,6 +3087,7 @@
   "application-operations": {
     "exports": ["./application/operations"],
     "modules": [
+      "src/globe/cesium/credits.js",
       "src/services/groundSnap.js",
       "src/globe/contract.js",
       "src/annotations/annotationResolver.js",