feat(commands-queue): Add method to wait for in-flight commands to complete

- Introduced `waitForInflightCommandsToComplete` method to asynchronously wait for all in-flight commands to finish processing.
- Utilized the `empty` event from `#waitingForReply` to signal when all commands have been completed.

Author: nkaradzhov

packages/client/lib/client/commands-queue.ts

@@ -138,6 +138,17 @@ export default class RedisCommandsQueue {
     this.#pushHandlers.push(handler);
   }
 
+  async waitForInflightCommandsToComplete(): Promise<void> {
+    // In-flight commands already completed
+    if(this.#waitingForReply.length === 0) {
+      return
+    };
+    // Otherwise wait for in-flight commands to fire `empty` event
+    return new Promise(resolve => {
+      this.#waitingForReply.events.on('empty', resolve)
+    });
+  }
+
   addCommand<T>(
     args: ReadonlyArray<RedisArgument>,
     options?: CommandOptions