For docker compatibility we need to support --platform
flag.
podman create --platform
podman run --platform
podman pull --platform
Since we have --override-os and --override-arch already
this can be done just by modifying the client to split
the --platform call into os and arch and then pass those
options to the server side.
Fixes: https://github.com/containers/podman/issues/6244
Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>