Separate command to specify the folder (directory) with user workflows

### Feature Idea

Reopening the request: https://github.com/comfyanonymous/ComfyUI/issues/5652
And the continuation of this request: https://github.com/Comfy-Org/ComfyUI_frontend/issues/688

We really need separate command for a completely separate directory for storing workflows.
As an example, I would like to have the command "**--workflows-directory**"

Arguments:
- We would like to keep user settings for different ComfyUIs in the system in separate folders, while storing workflows in a single global folder.
- User settings for different ComfyUIs sometimes conflict.
- For third-party wrapper applications, it would be convenient to create a more flexible ComfyUI configuration for users, specifying more specific folders for storing workflows or settings.
- In the future, when ComfyUI uses subgraphs as separate files (that is, a subgraph is stored in one specific folder and used in multiple other workflows (files)), it would be highly desirable to have this global folder containing workflows, separated from user settings and other non-workflow-related files and configurations.

### Existing Solutions

Currently, there's a command called "**--user-directory**", which allows you to specify a user directory where user data (ComfyUI settings, interface settings, custom nodes, and user workflows) will be stored.

However, this command doesn't allow you to separate the workflow folder from the user settings. This creates some problems if different versions of Comfy are used with different settings, but the user attempts to use a single (global) workflow folder.

### Other

I currently have a case that prevents me from doing my work efficiently and conveniently:
I'd like to have different settings for the different ComfyUI's I have, but I'd like them all to link to a single workflow folder. I need this for custom node development, or simply for different ComfyUI use cases (for example, one ComfyUI with specific settings for client demonstrations, and a second ComfyUI for development with a cluttered interface, different settings, and a different set of custom nodes (with different settings).