Allow Podman to pull machine images based on configuration defined in c/common instead of hardcoding the machine OS origin in Podman. This will centralize machine image configuration and make it easier to manage across the container ecosystem.

This story involves:

• Updating Podman to only use c/common configuration for machine image pulling
• Removing hardcoded machine OS origins from Podman
• Updating documentation to reflect the configuration change
• Adding tests to validate machine image pulling using c/common configuration