fix: UniqueKey does not work for controller tag when building app on release mode in Flutter 3.22

[TinhHuynh]

Hi, the PodPlayerController uses UniqueKey().toString() to generate a tag for the internal PodGetXController. However, in Flutter 3.22, there is an issue that UniqueKey always returns "Instance of UniqueKey" in release mode. No matter how many PodPlayerController are created, they still share the same PodGetXController instance.

To address this issue, I've replaced the usage of UniqueKey with Uuid for tag generation in the PodPlayerController class. Uuid is a safer and more standard approach for generating unique identifiers, and it ensures that each PodPlayerController instance will have a unique tag.

This change affects the _init method in the PodPlayerController class, where the getTag variable is assigned. I've tested the changes and confirmed that each PodPlayerController instance now receives a unique PodGetXVideoController instance as expected.