feat: implement origin detection

[darccio]

What does this PR do?

Origin Detection is a feature that allows the Agent to correctly detect and tag incoming custom metrics or traces with their Origin (AKA container tags).

Origin Detection works by having the client sending additional data to the Agent so the Agent is able to resolve the Origin.

This PR implements the missing external data implementation. External data was implemented as a last resort for Origin Detection in case no other solution would work.

It also updates the cid- prefix for the container ID according to the current state of Origin Detection as described in the task's RFC.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.
• For internal contributors, a matching PR should be created to the v2-dev branch and reviewed by @DataDog/apm-go.

Unsure? Have a question? Request a review!

[datadog-datadog-prod-us1]

Datadog Report

Branch report: dario.castane/langplat-286/origin-detection
Commit report: b6d7792
Test service: dd-trace-go

✅ 0 Failed, 5222 Passed, 73 Skipped, 1m 55.7s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-02-05 15:17:35

Comparing candidate commit 2c8524e in PR branch dario.castane/langplat-286/origin-detection with baseline commit 829de1b in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 58 metrics, 1 unstable metrics.

[darccio]

system-Tests covering this feature are in progress, but I'm waiting on some help as this feature depends on environment variables and it doesn't seem to be a good way to test these cases in system-tests. Also, the related headers seem to be not properly tested.

[rarguelloF]

LGTM!