Podman 6: machine usability improvements

Podman 6 introduces significant usability improvements to its machine functionality by reducing the prominence of provider selection for users. Key changes include the ability to manage machines by name alone regardless of their provider (eliminating the need for provider-specific commands), displaying all machines across all providers by default, and a new `--provider` flag for the `podman machine init` command to easily create machines with non-default providers. These updates aim to simplify the user experience when working with multiple virtual machine providers across different platforms.