Complete carousel refactor.

Reduces one layer of DOM nesting for simplication, uses the latest Embla
version, unittests for everything.

tests/camera-manager/range.test.ts

@@ -135,6 +135,7 @@ describe('compressRanges', () => {
       compressRanges([
         { start: now, end: nowPlusOne },
         { start: nowPlusOne, end: nowPlusTwo },
+        { start: now, end: nowPlusOne },
       ]),
     ).toEqual([{ start: now, end: nowPlusTwo }]);
   });
@@ -162,4 +163,8 @@ describe('compressRanges', () => {
     ];
     expect(compressRanges(input)).toEqual([{ start: 1, end: 3 }]);
   });
+
+  it('should return nothing with no input', () => {
+    expect(compressRanges([])).toEqual([]);
+  });
 });