Migrate bootc dependency from containers image proxy to podman

[harche]

Currently, bootc relies on containers image proxy crate to pull images. However, looking at the shortcomings of the container image proxy, we have decided to replace it with podman.

This issue is to track the required effort.

/cc @vrothberg @cgwalters

[harche]

Notes -

Might use this library - https://docs.rs/podman-api/0.10.0/podman_api/api/struct.Images.html#method.pull

[vrothberg]

/cc @rhatdan

[rhatdan]

I am fine with this. But does this put a requirement on having podman installed as a service and socket enabled in order to run bootc.

[harche]

@rhatdan it seems from @cgwalters's PR in this area, he is going to execute a podman command, so it doesn't seem like socket is necessary.

[rhatdan]

So bootc will require podman be installed, which is probably fine.