Deprecate all toolbox containers that don't use a reflexive entry point

Toolbox containers created prior to commit 8b84b5e460 didn't use
'toolbox init-container' as their entry points. This prevents them
from being configured at runtime through the entry points.

Being able to configure a toolbox container at runtime through the
entry point is very handy, as compared to doing it statically via
'podman create', because the configuration doesn't get permanently
baked into the container's definition. Instead, it's codified in
toolbox(1), which can be updated over time, and the container
reconfigured everytime it's started.

A deprecation notice is the precursor to actually dropping support for
these old containers in the future.

Preliminary testing suggests that toolbox containers created prior to
commit 8b84b5e460 already don't start on cgroups v2 systems. So,
this is mainly targetted at cgroups v1 users, who are still able to
work with those old containers.

https://github.com/containers/toolbox/pull/336

toolbox

@@ -1486,6 +1486,9 @@ run()
                 exit 1
             fi
         done
+    else
+        echo "$base_toolbox_command: container $toolbox_container uses deprecated features" >&2
+        echo "Consider recreating it with Toolbox version 0.0.17 or newer." >&2
     fi
 
     if ! $podman_command exec --user root:root "$toolbox_container" touch /run/.toolboxenv 2>&3; then