Support loading encryption keys from an S3 bucket

[dlvenable]

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

I'd like to be able to get encrypted data keys from an S3 bucket. I want to list the objects in the bucket and then have them all available for encryption. However, I'd like to use the latest one by default.

Describe the solution you'd like

I'd like to build off of #5335 and support this as part of an encryption engine feature.

encryption:
   encryption_key_directory: s3://my-bucket/path/to/

Describe alternatives you've considered (Optional)

This could be moved to be controlled under the kafka buffer, but I'd rather do this in the proposed extension.

buffer:
  kafka:
    topics:
    - name: topicname
      encryption_key_directory: s3://data-plane-bucket/accountId/pipelineName/internalPipelineId/

Additional context

N/A