Support Consumer Group Policies in 3.4+

[mheap]

We need to support Consumer Group policies in decK until the next major Gateway version is released.

Based on the work I've done recently, searching for isConsumerGroupScopedPluginSupported in go-database-reconciler is a good starting point.

My recommendation is that we allow users to set something in _info e.g. _info.use_consumer_group_overrides: true. If this value is set, only rate-limiting-advanced plugins should be enabled for consumer groups. All other plugins should trigger an error.

There's also an enforce_consumer_groups option which might be worth investigating. I don't think we should reuse this field, but I also don't understand it's purpose for now and it would be good to understand.