Set default config for on-prem deployment

For Capella, control plane will set the config correctly for 7.2.1 as part of
https://couchbasecloud.atlassian.net/browse/AV-58958

By default, a couple of configs were enabled to facilitate testing. These need to be set to their correct default values for on-prem deployments.

"indexer.maxHeapThreshold", type integer (set to 0 by default).
"indexer.rebalance.enableEmptyNodeBatching", type boolean, default needs to be set to false