fix: make dev_reload work for files in nodes/

[keturn]

Summary

The dev_reload option to load Python changes on the fly should work for custom nodes as well as Invoke's own sources.

(Have y'all been trying to write nodes without this? Or do you have another hot-reloading mechanism you've been using instead?)

QA Instructions

1. have some code in a nodes/ subdirectory.
2. Run invoke with INVOKEAI_DEV_RELOAD=true environment variable. (Or set dev_reload = True in your `invokeai.yaml'.)
3. Run invokeai-web
4. Startup logs should include a [jurigged] Watch line for your nodes source.
5. When you edit that file, the log should include a [jurigged] Update line for it.

Merge Plan

N/A

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• N/A Tests added / updated (if applicable)
• N/A Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)

[keturn]

Alternatively, we could make load_custom_nodes explicitly communicate with jurigged, but this is easier and almost as effective.

The one gap is if someday in the future we change it so load_custom_nodes is called again later somewhere else.