Only fire setting changes for changed settings

Previously we were firing updates for everything, which is bad. This has an effect of causing the room list to update itself every time the user goes to toggle some account settings.

src/utils/arrays.ts

@@ -46,6 +46,28 @@ export function arrayDiff<T>(a: T[], b: T[]): { added: T[], removed: T[] } {
     };
 }
 
+/**
+ * Returns the union of two arrays.
+ * @param a The first array. Must be defined.
+ * @param b The second array. Must be defined.
+ * @returns The union of the arrays.
+ */
+export function arrayUnion<T>(a: T[], b: T[]): T[] {
+    return a.filter(i => b.includes(i));
+}
+
+/**
+ * Merges arrays, deduping contents using a Set.
+ * @param a The arrays to merge.
+ * @returns The merged array.
+ */
+export function arrayMerge<T>(...a: T[][]): T[] {
+    return Array.from(a.reduce((c, v) => {
+        v.forEach(i => c.add(i));
+        return c;
+    }, new Set<T>()));
+}
+
 /**
  * Helper functions to perform LINQ-like queries on arrays.
  */