fix(aws_kinesis sink): fix batching of requests #20575 #1407

[steven-aerts]

Send batches to AWS Kinesis Data Streams and AWS Firehose independent of ther parition keys. In both API's batches of events do not need to share the same partition key. This makes the protocol more efficient, as by default the partition key is a random key being different for every event.

I validated this commit locally, all unit tests are successful. Relying on CI for integration tests.