Zachg/rust tracer add datadog trace endpoints

[ZStriker19]

Motivation

We want the rust tracer to be able to pass datadog parametric system-tests to validate its behavior

Changes

This PR adds a skeleton for the datadog parametric endpoints as well as implements the span/start and span/finish endpoint. More endpoints will be implemented in time as we work to pass more of the tests.

It also enables passing sampling tests in the rust.yml file while skipping those that fail for the reason that we have not yet implemented lazy sampling in the rust tracer yet. Therefore any sampling decision that relies on metadata set after the span starts will not be correct.

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner.
   • Framework is modified, or non obvious usage of it -> get a review from R&P team

🚀 Once your PR is reviewed and the CI green, you can merge it!

🛟 #apm-shared-testing 🛟

Reviewer checklist

• If PR title starts with [<language>], double-check that only <language> is impacted by the change
• No system-tests internal is modified. Otherwise, I have the approval from R&P team
• A docker base image is modified?
  • the relevant build-XXX-image label is present
• A scenario is added (or removed)?
  • Get a review from R&P team