Modular backend - T2I Adapter

[StAlKeR7779]

Summary

T2I Adapter code from #6577.

Related Issues / Discussions

#6606
https://invokeai.notion.site/Modular-Stable-Diffusion-Backend-Design-Document-e8952daab5d5472faecdc4a72d377b0d

QA Instructions

Run with and without set USE_MODULAR_DENOISE environment.

Merge Plan

Nope.
If you think that there should be some kind of tests - feel free to add.

Checklist

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

[RyanJDick]

Just a few minor comments.

Manual tests to be completed before merging (I've completed a few already.):

• SDXL, Standard guidance, single T2I-Adapter
• SDXL, Standard guidance, multiple T2I-Adapters
• SDXL, Sequential guidance, single T2I-Adapter
• SDXL, Sequential guidance, multiple T2I-Adapters
  At leat one test with SD1 to make sure that both SDXL and SD1 are working:
• SD1, Standard guidance, single T2I-Adapter

[StAlKeR7779]

Just a few minor comments.

Manual tests to be completed before merging (I've completed a few already.):

• SDXL, Standard guidance, single T2I-Adapter
• SDXL, Standard guidance, multiple T2I-Adapters
• SDXL, Sequential guidance, single T2I-Adapter
• SDXL, Sequential guidance, multiple T2I-Adapters
  At leat one test with SD1 to make sure that both SDXL and SD1 are working:
• SD1, Standard guidance, single T2I-Adapter

Tried:

• SD1, Standard guidance, single T2I-Adapter
• SD1, Standard guidance, multiple T2I-Adapters
• SD1, Sequential guidance, single T2I-Adapter
• SD1, Sequential guidance, multiple T2I-Adapters
• SDXL, Standard guidance, single T2I-Adapter
• SDXL, Standard guidance, multiple T2I-Adapters
• SDXL, Sequential guidance, single T2I-Adapter
• SDXL, Sequential guidance, multiple T2I-Adapters