Cache Rules output inconsistent

The `cache list-cache-settings-rule` operation returns inconsistent structure when cache rules are defined vs when they are not:

### Cache Rules Exist

```
[
{
"action": "HTTP_CACHE_MAKE_STATIC",
"disabledByCacheMode": false,
"enabled": true,
"filter": "URL == \"/commons-9a37b461e14cdb912bf2.js\"",
"name": "Force cache",
"rule_id": 106200,
"ttl": 3600
}
]
```

### No Cache Rules

```
{
"debug_info": {
"Site has no Cache rules": "GET - /api/prov/v2/sites/***/settings/cache/rules/",
"id-info": "999999"
},
"res": 0,
"res_message": "OK"
}
```

Scripts can currently check for the existence of the `debug_info` key to determine if there are existing rules or not - however, if we restructure the output like the example below, the check for `debug_info` could be eliminated and we'd have a consistent output.

```
{
"rules" : [],
"debug_info": {
"Site has no Cache rules": "GET - /api/prov/v2/sites/***/settings/cache/rules/",
"id-info": "999999"
},
"res": 0,
"res_message": "OK"
}
```

Start at the `cache list-cache-settings-rule` operation and compare its output when cache rules exist with the output when none exist. The change is complete when the no-rules response includes a `rules` array alongside the existing `debug_info`, `res`, and `res_message` fields, matching the proposed structure.

Written by the indexing model from the issue text.