chore: custom impl for set.difference api (#19135)

web/src/lib/utils/timeline-util.ts

@@ -216,3 +216,13 @@ export const plainDateTimeCompare = (ascending: boolean, a: TimelinePlainDateTim
   }
   return aDateTime.millisecond - bDateTime.millisecond;
 };
+
+export function setDifference<T>(setA: Set<T>, setB: Set<T>): Set<T> {
+  const result = new Set<T>();
+  for (const value of setA) {
+    if (!setB.has(value)) {
+      result.add(value);
+    }
+  }
+  return result;
+}