Added tests for checking injection metadata

[sydney-tung]

Motivation

This PR was prompted by the addition of new injection metadata fields to telemetry forwarding for python.

Changes

Added new validation checks for injection metadata.

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

:rocket: 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