Review move to bridge PRs.

[mashhurs]

We have 2 BIG PRs need to be review for the full coverage of moving to the Logstash bridge.

• [logstash-bridge] Introduce GeoIp interfaces elasticsearch#132595
• Move to ES bridge API #336

Findings:

• GeoIP version conflict:
  • align bridge to yaauie/elasticsearch@94d58d47cd mashhurs/logstash-filter-elastic_integration#1
  • Logstash bridge refinement mashhurs/elasticsearch#2
• Improvements:
  • Migrate all Bridges to "interface pattern", using factory methods instead of constructors.
  • Extract implementations to package-private (so that we have a clear boundary of what is "externalized" to the logstash plugin