[EXPERIMENTAL] move propagator interfaces to ddtrace root

[GustavoCaso]

trafficstars

What does this PR do?

Motivation

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 Datadog employees:

• [ ] If this PR touches code that handles credentials of any kind, such as Datadog API keys, I've requested a review from @DataDog/security-design-and-guidance.
• [ ] This PR doesn't touch any of that.

Unsure? Have a question? Request a review!

[pr-commenter[bot]]

Benchmarks

Benchmark execution time: 2024-01-31 16:56:35

Comparing candidate commit fd5355648a5f36901a225e8e0edacb4ceb4f3a1b in PR branch extract-interfaces-for-datadog-agent-serverless with baseline commit 8c4834f24951876c7f50a98fa640a96541cc3c04 in branch main.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 38 metrics, 2 unstable metrics.

scenario:BenchmarkStartRequestSpan-24

• 🟥 execution_time [+8.920ns; +13.260ns] or [+2.259%; +3.358%]

[github-actions[bot]]

This PR is stale because it has been open 20 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[github-actions[bot]]

This PR was closed because it has been open for 30 days with no activity.