Implement a Quadlet generator that can create Quadlet unit files from existing containers. This will allow users to easily convert their running containers into systemd-managed Quadlet units.

This story involves:

• Implementing a command to generate Quadlet files from running containers
• Supporting all relevant container configuration options
• Creating a design document outlining the generator functionality
• Updating documentation to describe the Quadlet generator
• Adding tests to validate Quadlet generation from containers

Reference: Podman 6 High Level Design