Add the ability to retry on failure.

[roaksoax]

According to documentation,

By default, the client retries the request 3 times
But another doc says below in retry_on_failure section, which appears contradicting to me.

Whether to retry X times when request fails before raising and exception. Defaults to false.
Looking at the current implementation, it is not using retry_on_failure
https://github.com/logstash-plugins/logstash-filter-elasticsearch/blob/main/lib/logstash/filters/elasticsearch/client.rb#L36-L37