Correctly handle creating model index json files when setting compiled modules in pipelines.

[DN6]

What does this PR do?

Setting a pipeline component to a compiled module and then calling save_pretrained results in an incorrect model_index.json file being created for the pipeline. This is because the compiled module isn't unwrapped before registering to config.

This PR:

Moves a block of code in register_modules into a helper function that correctly unwraps the compiled module and extracts the correct library and class name. We can then apply this function everywhere that is needed to extract the library, class tuple.

So it should also handle pipeline modules like MultiControlNet.

Fixes # (issue)
#5617

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]

Nice refactor