Jaeger integration part 2

[simitt]

Since #2886 the APM Server can act as a basic Jaeger collector, allowing to receive and process Jaeger spans. As listed in the issue and in the docs it is an experimental feature.

In a next step the integration should be extended and remove some of the current caveats:

Add/Improve Logic:

• Auth handling
• Support Sampling
• Record additional Span Logs

End-to-end Testing:

• Add automated tests to CI, creating a test app instrumented by a jaeger agent sending data in expected format to ES ([Jaeger] Add setup for jaeger agent integration with APM Server via gRPC apm-integration-testing#679)
• Add automated tests to CI, creating a test app using the jaeger client sending data via thrift over http to the APM Server and ingesting in expected format to ES ([Jaeger] Add setup for jaeger client integration with APM Server via thrift over http apm-integration-testing#680)

[axw]

Moving to backlog until we have logs/events support, there's a separate issue for sampling.

[axw]

Closing this since we have support for sampling and auth now, and issues for the remaining things.