Re-use cluster.queryServiceMemoryQuota

Just realised that we already have couchbaseclusters.spec.cluster.queryServiceMemoryQuota, which does nothing to Couchbase Server (as there was no previous option to set a per-node quota), but is used to determine Pod resource requirements.

I think the right thing to do here is to keep the existing spec.cluster.queryServiceMemoryQuota and use that value to set queryNodeQuota in 7.6+ (as well as for determining Pod resource requirements), and to remove spec.cluster.query.NodeQuota.

Given that we're now presenting it as a top-level cluster setting in the 7.6 docs, I think it makes sense to have a single top-level quota value for the Query Service - having both will cause confusion (and possibly issues if they are set to wildly different values).