refactor(ui): remove the map stack chip DOM builders

The dock renders the chips from the map source controls' published view,
so renderMapStackChips, syncMapStackChips and MAP_STACK_CHIP_CLASS have no
callers. Their tests now pin the chip models; the dock test keeps the
rendered chips' button type and native enablement.

src/ui/commandDock.test.mjs

@@ -127,6 +127,11 @@ test('the map source row renders the published chips and selects through the con
   );
   const [bing, esri, osm] = chips;
   assert.equal(bing.classList.contains('unavailable'), true);
+  assert.equal(
+    bing.disabled,
+    false,
+    'unavailable chips stay keyboard-reachable',
+  );
   assert.equal(bing.getAttribute('aria-disabled'), 'true');
   assert.equal(
     bing.getAttribute('aria-label'),

src/ui/mapSource.js

@@ -1,9 +1,6 @@
 export { createMapSourceControls } from './mapSourceControls.js';
 export {
-  MAP_STACK_CHIP_CLASS,
   PRESENTED_MAP_STACK_IDS,
   mapStackChipModel,
   mapStackChipModels,
-  renderMapStackChips,
-  syncMapStackChips,
 } from '../mapStackChips.js';