parametric: Ensure start span endpoints align with the spec

[mabdinur]

Motivation

• Ensure the arguments supplied to the start span parametric endpoint are equivalent to the arguments expected by the Tracer.start_span (in most languages).

Changes

• Adds extract_header endpoint to all parametric apps defined in the the system-tests repo (so not c++)
• Adds a test case for the new extract_header endpoints in parametric_endpoint_parity feature.
• Removes HttpHeader extraction from the start span endpoint
• Removes links and origin arguments from start span.
  • dd_origin should be set using the new extract_headers endpoint via http headers (and not by start_span).
  • links should be added using the add_link endpoint. Most tracers do not support creating spans with links
• Updates all distributed tracing tests to use extract_header API (instead of using start_span + http_headers argument)
• Updates all tests that initialize a span with origin and links.

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes (if something not related to your task is failing, you can ignore it)
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner. We're working on refining the codeowners file quickly.
   • Framework is modified, or non obvious usage of it -> get a review from R&P team

🚀 Once your PR is reviewed, 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
• CI is green, or failing jobs are not related to this change (and you are 100% sure about this statement)
• 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

[cbeauchesne]

From framework usage, AGTM. But to do a proper review, could you ask to someone familiar with the tested feature ?

[khanayan123]

Outside of a minor nit. LGTM

[ZStriker19]

From a Python tracer and system-tests perspective looks great! Awesome work!

[mtoffl01]

Fine from my side, although have a question about new spanContexts field on apmClientServer.

[cbeauchesne]

Framework usage: all good.