[Tracing] Implement initial weblog tests for the runtime metrics feature

[zacharycmontoya]

"dogstatsd_non_local_traffic: true" to the agent image and start testing runtime metrics by observing what metrics the agent is sending to the backend

Motivation

We need to assert some basic functionalities of the Runtime Metrics feature across various tracing libraries.

Changes

• Adds the config dogstatsd_non_local_traffic: true to the Datadog agent container
• Adds a method in the Agent interface to get the metrics it submits to the /api/v2/series backend API
• Implements new tests in classes Test_Config_RuntimeMetrics_Enabled and Test_Config_RuntimeMetrics_Enabled_WithRuntimeId. Each test case hits an endpoint, waits 10s (that is the default interval for submitting runtime metrics), and asserts properties of the submitted metrics

The end result is that the .NET Tracer and the Java Tracer are fully passing the initial tests

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