docker info: expose runtime features ("rro" mount mode, etc.)
Fix issue 46580
```console
$ curl -s --unix-socket /var/run/docker.sock http://docker/v1.44/info | jq .Runtimes
{
"crun": {
"path": "/usr/local/bin/crun",
"status": {
"org.opencontainers.runtime-spec.features": "{\"ociVersionMin\":\"1.0.0\",...}"
}
},
"io.containerd.runc.v2": {
"path": "runc",
"status": {
"org.opencontainers.runtime-spec.features": "{\"ociVersionMin\":\"1.0.0\",...}"
}
},
"runc": {
"path": "runc",
"status": {
"org.opencontainers.runtime-spec.features": "{\"ociVersionMin\":\"1.0.0\",...}"
}
},
"runsc": {
"path": "/usr/local/bin/runsc"
}
}
```
Co-authored-by: Sebastiaan van Stijn <github@gone.nl>
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
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