[Fargate] [request]: Support Datadog output for fluentbit configuration

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**Tell us about your request**
What do you want us to build?
add datadog output in fluentbit. Datadog output plugin is supported by fluentbit from v0.13, and is it not support by aws-observability.
https://docs.aws.amazon.com/ja_jp/eks/latest/userguide/fargate-logging.html

**Which service(s) is this request for?**
This could be Fargate, EKS.

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
What outcome are you trying to achieve, ultimately, and why is it hard/impossible to do right now? What is the impact of not having this problem solved? The more details you can provide, the better we'll be able to understand and solve the problem.
We want to use aws-observability to collect logs and send logs to Datadog. But is is not support by aws-observability.

**Are you currently working around this issue?**
How are you currently solving this problem?
Yes, if possible.

**Additional context**
Anything else we should know?

**Attachments**
If you think you might have additional information that you'd like to include via an attachment, please do - we'll take a look. (Remember to remove any personally-identifiable information.)

The issue names AWS Fargate/EKS, Fluent Bit, and the Datadog output plugin, but no repository files, tests, or implementation entry point. Start by locating the aws-observability Fluent Bit configuration and its supported outputs; done means logs can be collected and sent to Datadog through the supported configuration.

Written by the indexing model from the issue text.