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

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• 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]

💚 CLA has been signed