Some multi-bucket aggs cannot be used in pipeline aggs

[jetnet]

Elasticsearch version: 7.6
Plugins installed: [ingest-attachment, ingest-opennl]

JVM version : openjdk version "13.0.2" 2020-01-14

OS version : Windows 10

Description of the problem including expected versus actual behavior:
Filter Agg and IP Range Agg cannot be used as a source for Pipeline Aggs

Steps to reproduce:
Example with the ip_range agg:

GET an_ECS_index/_search
{
  "size": 0,
  "aggs": {
    "1-bucket": {
      "ip_range": {
        "field": "destination.ip",
        "ranges": [
          {
            "mask": "192.168.0.0/16"
          },
          {
            "mask": "10.10.0.0/16"
          }
        ],
        "keyed": false
      }, 
      "aggs": {
        "1-metric": {
          "sum": {
            "field": "source.bytes"
          }
        }
      }
    },
    "1": {
      "sum_bucket": {
        "buckets_path": "1-bucket>1-metric"
      }
    }
  }
}

Error:

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "The first aggregation in buckets_path must be a multi-bucket aggregation for aggregation [1] found :org.elasticsearch.search.aggregations.bucket.range.IpRangeAggregationBuilder for buckets path: 1-bucket>1-metric"
      }

The similar error occurs when using filter agg.

[martijnvg]

This originated from a discuss topic.

[elasticmachine]

Pinging @elastic/es-analytics-geo (:Analytics/Aggregations)

[polyfractal]

Also includes filter agg (#14600), or really any bucketing agg that doesn't directly extend MultiBucket

[nik9000]

``filter` intentionally isn't a multi-bucket agg - it is a "single bucket" agg. #54161 just fixes the aggs that is looks like we "forgot". If we want to be able to operate on single bucket aggs we certainly can, but I don't want to sneak that change in with a fix for this.