[Feature Request]: Manage node templates in workflow sidebar tab

### Is there an existing issue for this?

- [X] I have searched the existing issues and checked the recent builds/commits

### What would your feature do ?

Replace the current node template management system with an extra folder in workflow sidebar tab.

### Proposed workflow

- Open workflow sidebar tab
- See a folder with a different icon and name `Templates` for current node templates

### Additional information

- Exsiting node template management should be removed.
- User should still be able to add template via the context menu.
- Storage of templates are converted to normal workflow format and save in `workflows/Templates/` directory

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-1801-Feature-Request-Manage-node-templates-in-workflow-sidebar-tab-15f6d73d365081f88c21e2bb88444456) by [Unito](https://www.unito.io)