[Add] VEnhancer - the interpolation and upscaler for CogVideoX-5b

### Model/Pipeline/Scheduler description

VEnhancer, a generative space-time enhancement framework that can improve the existing T2V results.

https://github.com/Vchitect/VEnhancer

### 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

_No response_

Start by reading the VEnhancer implementation and model-weight links in the issue, then compare them with the repository's existing CogVideoX-5b pipeline integrations. The work is complete when VEnhancer is available as an interpolation and upscaling addition for CogVideoX-5b, with behavior matching the upstream implementation.

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