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.

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: 2d3c990
Test service: dd-trace-go

✅ 0 Failed, 5216 Passed, 73 Skipped, 2m 27.99s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-01-28 16:58:21

Comparing candidate commit 3ece399 in PR branch dario.castane/langplat-286/origin-detection with baseline commit 599da51 in branch main.

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

scenario:BenchmarkSetTagString-24

• 🟥 execution_time [+3.482ns; +5.338ns] or [+3.113%; +4.773%]