Transfer generation parameters to previews

[SirFrags]

Describe what this pull request is trying to achieve.

If generation parameters are automatically saved to pngs, the "replace preview" feature in extra networks does not currently copy them to the preview image.

Additional notes and description of your changes

Modifies ui_extra_networks.py / setup_ui to additonaly copy parameters if they exist.

Environment this was tested in

List the environment you have developed / tested this on. As per the contributing page, changes should be able to work on Windows out of the box.

• OS: Windows
• Browser: Chrome
• Graphics card: NVIDIA RTX 3090 24GB

Screenshots or videos of your changes

N/A, no UI changes.

[muerrilla]

This is a good workaround for saving model trigger words.