Add Firehose output

[pierredeman]

Release notes

Add firehose output plugin

What does this PR do?

Send events to firehose with AWS SDK and the put_record_batch method.
Events will be sent in batches, following the base multi_receive_encoded method.
If number or size of events exceeds the AWS limits, sub-batches will be created.
The limits can be overriden by the users and they must define at least a delivery_stream_name configuration.

Checklist

• [x] My code follows the style guidelines of this project
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] I have made corresponding change to the default configuration files (and/or docker env variables)
• [x] I have added tests that prove my fix is effective or that my feature works

How to test this PR locally

1. Use following config

   input {
   stdin {}
   }
   output {
   firehose {
   # Use your prefered authentication method
   region => "${YOUR_REGION}"
   access_key_id => "${YOUR_ACCESS_KEY}"
   secret_access_key => "${YOUR_SECRET_KEY}"
   # Define a kinesis data firehose stream to test your events
   delivery_stream_name => "test-stream"
   }
   }

2. Send some input data
3. Verify all is received by firehose

[cla-checker-service[bot]]

💚 CLA has been signed