[python] add test for suspicious import errors

[christophe-papazian]

Motivation

A suspicious import error was found in some system tests logs. This is related to a bad interaction between gevent and ctypes leading to an import failure when the appsec processor or the api manager is loaded.
This was fixed by DataDog/dd-trace-py#11987

As is seems to only be detectable through end to end test with a gunicorn based weblog, a system test was needed to add a regression test.

Changes

• add a scenario for language specific tests
• add a test file for python only tests, with a specific class test checking for import error through the circular import message on stderr
• enable the new test for python on v2.20.0.dev. The test is currently failing on all gunicorn based weblog on prod, as expected.

APPSEC-56449

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]

Just two lines to remove, then all good