[WEB-2884] chore: Update timezone list, add new endpoint, and update timezone dropdowns (#6231)

* dev: updated timezones list

* chore: added rate limiting

web/core/services/timezone.service.ts

@@ -0,0 +1,23 @@
+import { TTimezones } from "@plane/types";
+// helpers
+import { API_BASE_URL } from "@/helpers/common.helper";
+// api services
+import { APIService } from "@/services/api.service";
+
+export class TimezoneService extends APIService {
+  constructor() {
+    super(API_BASE_URL);
+  }
+
+  async fetch(): Promise<TTimezones> {
+    return this.get(`/api/timezones/`)
+      .then((response) => response?.data)
+      .catch((error) => {
+        throw error?.response?.data;
+      });
+  }
+}
+
+const timezoneService = new TimezoneService();
+
+export default timezoneService;