UI Mode for Workflows

### Feature Idea

Casual, not-technical users can find the node-based workflows of ComfyUI a bit scary and hard to understand. However, *using* an existing workflow can be as easy as changing a few parameters. I propose adding a "UI Mode" to workflows to allow ComfyUI power users to make image generator "Apps" that can then be shared with non-technical users.

Feature details:

- Add a ui/node view toggle to the menus
- Add "Hide in UI" parameter to nodes
- Add ui-specific positioning variables to nodes
- Add a "Default view" parameter to workflows

When the node view is active, the user sees the standard ComfyUI node view. When the ui view is active, the connections between nodes are hidden as well as any nodes that have the "Hide in UI" parameter set. The workflow creator can then re-arrange the remaining visible nodes into a user-friendly arrangement that is independent of the node view arrangement.

Once the workflow and ui are complete, the workflow creator can set the default view of the workflow to "UI" and share it with non-technical users, who will see the UI view when they load the workflow. They can then use the workflow as an app without needing to worry about the details of how it works.

Also, to make using workflows more seamless for technical and non-technical users alike, ComfyUI could also be updated to automatically download missing custom nodes and/or models needed by the workflows after getting the user's approval.

### Existing Solutions

_No response_

### Other

_No response_