[ECS] [AWS for Fluent Bit]: Support ECS Task metadata injection when running Fluent Bit as a Daemon Service

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**Tell us about your request**

Support ECS Task metadata injection when running Fluent Bit as a Daemon Service. FireLens can inject metadata but it requires running Fluent Bit as a sidecar. There is no nice way to inject task metadata in logs when running Fluent Bit as a daemon.

**Which service(s) is this request for?**
ECS

The issue mentions ECS, Fluent Bit, FireLens, and daemon services but names no repository files, tests, or entry points. Start by researching ECS task metadata injection and the differences between daemon and sidecar deployments. Define the supported metadata, configuration path, and validation criteria before implementation; done means task metadata appears reliably in daemon-service logs.

Written by the indexing model from the issue text.