[7.x] Network community_id processor for ingest pipelines (#66534)

[danhermann]

Adds a processor that computes the community_id for flow data according to the Community ID Specification.

For example:

POST _ingest/pipeline/_simulate?verbose
{
  "pipeline": {
    "processors": [
      {
        "community_id": {
        }
      }
    ]
  },
  "docs": [
    {
      "_source": {
        "source": {
          "ip": "128.232.110.120",
          "port": 34855
        },
        "destination": {
          "ip": "66.35.250.204",
          "port": 80
        },
        "network": {
          "transport": "TCP"
        }
      }
    }
  ]
}

populates the network.community_id field as below:

...
"_source" : {
  "destination" : {
    "port" : 80,
    "ip" : "66.35.250.204"
  },
  "source" : {
    "port" : 34855,
    "ip" : "128.232.110.120"
  },
  "network" : {
    "community_id" : "1:LQU9qZlK+B5F3KDmev6m5PMibrg=",
    "transport" : "TCP"
  }
}
...

Closes #55685

Backport of #66534

[elasticmachine]

Pinging @elastic/es-core-features (Team:Core/Features)

[danhermann]

@elasticmachine update branch