ControlNeXt support

[lgleim]

Is your feature request related to a problem? Please describe.
ControlNeXt claims to improve control, generation performance & reduce VRAM requirements while maintaining or improving fidelity

Describe the solution you'd like
Integration of ControlNeXt in addition / instead of the current ControlNet integration

Describe alternatives you've considered
Stick with the current working implementation. I'm impartial but if ControlNeXt proves superior, the project may benefit

Additional context
Project page: https://pbihao.github.io/projects/controlnext/index.html
Code: https://github.com/dvlab-research/ControlNeXt
Paper: https://arxiv.org/abs/2408.06070