Add image and repo defaults for podman machine

[n1hility]

This PR adds a new platform driven user setting used by the draft PR containers/podman#12503

Additionally it modifies "image" to also have a platform driven default.

[Luap99]

You have to documents this in https://github.com/containers/common/blob/main/docs/containers.conf.5.md and add the fields to the default config https://github.com/containers/common/blob/main/pkg/config/containers.conf

[n1hility]

You have to documents this in https://github.com/containers/common/blob/main/docs/containers.conf.5.md and add the fields to the default config https://github.com/containers/common/blob/main/pkg/config/containers.conf

Oops sorry I missed that

[Luap99]

LGTM

[rhatdan]

/approve
/lgtm

[openshift-ci]

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