Split up latent.py (code reorganization, no functional changes)

[RyanJDick]

Summary

I've started working towards a better tiled upscaling implementation. It is going to require some refactoring of DenoiseLatentsInvocation. As a first step, this PR splits up all of the invocations in latent.py into their own files. That file had become a bit of a dumping ground - it should be a bit more manageable to work with now.

This PR just re-organizes the code. There should be no functional changes.

QA Instructions

I've done some light smoke testing. I'll do some more before merging. The main risk is that I missed a broken import, or some other copy-paste error.

Checklist

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

[blessedcoolant]

Maybe just rename latents.py to denoise_latents.py then? Rest of it seems good. This file needed to be decoupled.

[RyanJDick]

Maybe just rename latents.py to denoise_latents.py then? Rest of it seems good. This file needed to be decoupled.

Good point. Renamed in 68ab579

[lstein]

Looks great. I'd simply suggest changing latent.py to denoise_latents.py in order to be consistent with the naming scheme.

[edit] I see blessedcoolant had the same suggestion; did that commit just go through as I was reviewing?

[lstein]

I see the change to latents.py now. Approved.

[skunkworxdark]

The import path for SchedulerOutput in the invocation_api needs to be changed
it should be changed from

from invokeai.app.invocations.denoise_latents import SchedulerOutput

to

from invokeai.app.invocations.scheduler import SchedulerOutput