Enable offline single file model loading

[lstein]

Summary

This PR bumps diffusers to v0.30.0 and reenables the ability to load main checkpoint models without a connection to the internet.

Related Issues / Discussions

Closes #6623.

QA Instructions

1. Test generation with sd-1, sd-2 and sdxl models.
2. Test controlnet guidance
3. Test ti-adapter guidance
4. Test ip-adapter guidance
5. Test model loading when internet not connected.

Merge Plan

Given that this introduces the two regressions noted above, we should discuss whether to merge now or wait until the issue is fixed in diffusers.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• Documentation added / updated (if applicable)

[RyanJDick]

Link to the diffusers issue for reference: huggingface/diffusers#9171

[lstein]

The issue with v_prediction vs epsilon has been worked-around.
The issue with unconvertible sd 1.5 controlnets has been worked-around.
Loading of SDXL controlnet single files still does not work.

[brandonrising]

I ran an sd1 controlnet as a single file and it didn't seem to break as a result of this, but it seems weird to have this hard coded filepath here

[lstein]

The _name_or_path field is ignored during file conversion, but these fields will be removed.

[brandonrising]

Are you still following this PR @lstein ? I can take it over and get it across the line if you'd like

[lstein]

Are you still following this PR @lstein ? I can take it over and get it across the line if you'd like

I’m very happy to see renewed activity on this PR. I thought it was comatose. I’ll take it across the finish line.

[lstein]

Are you still following this PR @lstein ? I can take it over and get it across the line if you'd like
@brandonrising
I've removed the absolute path name from the controlnet json file and have corrected a merge conflict. Should be ready for a re-review.