[WIP] AnimateDiff + ControlNet

[charchit7]

What does this PR do?

Adding AnimateDiffControlNetPipeline pipeline to the diffusers!
Fixes #5866

Done:

• added the skeleton file to start with.

current TODO:

• understand the animatediff and controlnet codebase.
• improve the PR with recent progress.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Was this discussed/approved via a GitHub issue or the forum? Please add a link to it if that's the case.
• Did you make sure to update the documentation with your changes? Here are the
  documentation guidelines, and
  here are tips on formatting docstrings.
• Did you write any new necessary tests?

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

[patrickvonplaten]

Can we please add this as a community pipeline: https://github.com/huggingface/diffusers/tree/main/examples/community

[charchit7]

Sure @patrickvonplaten, I'll make changes for it.

[charchit7]

Solved In : #5928