[EDOT Collector] Allow Elastic Agent to run in hybrid mode

[ycombinator]

Describe the enhancement:

Elastic Agent should be able to run in hybrid mode — that is, it should be able to accept a policy containing OTel Collector configuration, start up an embedded OTel Collector, and pass the OTel Collector configuration from the policy to the embedded OTel Collector.

Describe a specific use case for the enhancement or feature:

To be able to run "classic" Elastic Agent configuration and OTel Collector configuration concurrently, to allow a more seamless transition from the former to the latter.

What is the definition of done?

Elastic Agent should be able to:

• accept a policy containing OTel Collector configuration
• start up an embedded OTel Collector, and
• pass the OTel Collector configuration from the policy to the embedded OTel Collector