CLI / REST commands to edit indexer settings only apply to FDB

The commands to modify indexer storage settings such as index-max-rollback-points and index-stable-snapshot-interval provided in both the couchbase-cli setting-index docs and the /settings/indexes REST API docs only change the settings for the Forest DB storage engine, which is only used by Couchbase Server CE. It will not have any effect for Couchbase EE users as the Indexer uses MOI or Plasma storage engines.

We should:

• Mention that changing these settings will only be applied if the user is on Couchbase CE.
• Expose the couchbase-cli and REST API commands to change these settings for Couchbase EE (if required).
• Update the corresponding links in the Index Snapshots and Index Rollback document.