Update the Behaviour of Indexer api/v1/stats endpoint.

As of today
api/v1/stats endpoint (without any bucket or scope or collection specified) will return stats for all the indexes only if user has "Query System Catalog" privileges. Else will not return any stats.

After change MB-45446
api/v1/stats endpoint (without any bucket or scope or collection specified) will return stats for all the indexes in Bucket, Scope, Collection for which user has "Query Manage Index" Permissions for even if he does not have "Query System Catalog" privileges to get stats for all indexes.

curl -u user1:asdasd http://localhost:9102/api/v1/stats
Will now return stats for the indexes which user1 has "Query Manage Index" Permissions for. It will return stats for all the indexes if user1 has "Query System Catalog" permission.