Parameters accepted by the aggregator include:
* prefix_length (integer, required): defines the network size of the subnet mask;
* is_ipv6 (boolean, optional, default: false): defines whether the prefix applies to IPv6 (true) or IPv4 (false) IP addresses;
* min_doc_count (integer, optional, default: 1): defines the minimum number of documents for a bucket to be returned in the results;
* append_prefix_length (boolean, optional, default: false): defines if the prefix length is appended to the IP address key when returning results;
* keyed (boolean, optional, default: false): defines whether the result is returned keyed or as an array of buckets;
Each bucket returned by the aggregator represents a different subnet. IPv4 subnets also include a netmask field set to the subnet mask value (i.e. "255.255.0.0" for a /16 subnet).
Related to: #57964 and elastic/kibana#68424
