[Functionbeat] Add support for AWS Kinesis record deaggregation

[jpaskhay]

Describe the enhancement:
FunctionBeat does not currently handle the Kinesis aggregated record format, which is commonly used to improve throughput and cost savings with AWS Kinesis. It should be updated to handle consumer deaggregation appropriately so that users can take advantage of the optimization.

Describe a specific use case for the enhancement or feature:
Producers sending in high throughput of small messages (< 1KiB) are likely to use aggregated records to help improve throughput and cost savings. Potential cost savings are largest if they happen to use Kinesis Data Firehose for other Kinesis sinks (e.g. S3) due to the "rounding up" of costs to nearest 5KiB (at the time of this writing).

I'll be submitting a PR for this feature, which has also been built and tested/verified in a local AWS account end to end.

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)