Add more attributes for elasticsearch rest client [5.10, 7.16).

[h0cheung]

Is your feature request related to a problem? Please describe.

For rest client in elasticsearch [5.0, 7.16), very poor informations are extracted in the spans:

• name: "POST"
• db.system: "elasticsearch"
• http.method
• http.url
• server.address
• server.port

Many useful attributes, such as db.operation.name, db.collection.name, db.namespace, are missing.

Describe the solution you'd like

We can instrument the rest high level client. By getting the high level ActionRequest, we can get db.operation.name and db.collection.name (indices) easily.

There is an implementation in the Skywalking javaagent, which seems good: https://github.com/apache/skywalking-java/tree/main/apm-sniffer/apm-sdk-plugin/elasticsearch-6.x-plugin

Describe alternatives you've considered

Maybe another way is trying to parse the URLs. Once a URL is successfully parsed, we can get db.operation.name and db.collection.name easily.

Additional context

I didn't found a good way to get the db.namespace, which should be the name of Elasticsearch cluster.