Add support for PPVCtrl

### Model/Pipeline/Scheduler description

I recently came across an impressive work called PPVCtrl, a controllable video generation model. It leverages an auxiliary condition encoder to transform a text-to-video generation model into a customizable video generator, all without retraining the original generator. It's akin to ControlNet, but for video generation.

Prompt
Reference Image
Control Videos
PP-VCtrl-5B-T2V
PP-VCtrl-5B-I2V




Group of fishes swimming in aquarium.






A boat with a flag on it is sailing on the sea.

Prompt
Reference Image
Control Videos
PP-VCtrl-5B-T2V
PP-VCtrl-5B-I2V




A rider in a dark helmet and white breeches is atop a chestnut horse...






A dark gray Mini Cooper is parked on a city street...

Prompt
Reference Image
Pose Videos
PP-VCtrl-5B-I2V




A young man with curly hair and a red t-shirt featuring a white logo is seen in various states of motion...











A woman models an Adrianna Papell women's gown, featuring a sleeveless...

### Open source status

- [x] The model implementation is available.
- [x] The model weights are available (Only relevant if addition is not a scheduler).

### Provide useful links for the implementation

https://github.com/PaddlePaddle/PaddleMIX/tree/develop/ppdiffusers/examples/ppvctrl

Inizia esaminando l’implementazione di PPVCtrl e gli esempi in ppdiffusers/examples/ppvctrl, quindi confronta i suoi componenti con le integrazioni esistenti per la generazione video in diffusers. Conferma la pipeline richiesta, i pesi del modello e il comportamento degli esempi prima di definire i test; il lavoro è completato quando il supporto per PPVCtrl è integrato e gli esempi documentati vengono eseguiti.

Scritto dal modello di indicizzazione a partire dal testo della issue.