PROF-9791: Allow None as default for profiling_enabled

[szegedi]

Motivation

This fixes a test failure with https://github.com/DataDog/dd-trace-js/pull/4322. That PR modifies the default for profiling_enabled in our Node.js tracer from false to undefined as for SSI-enabled profiling we need the ability to distinguish between explicitly specified DD_PROFILING_ENABLED=false env var and DD_PROFILING_ENABLED not being set; now the undefined value represents this latter condition.

Changes

Adds None to the list of acceptable values. Note this is rather analogous to 05b08aa (#2172).

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

:rocket: Once your PR is reviewed, you can merge it!

🛟 #apm-shared-testing 🛟

Reviewer checklist

• [ ] Relevant label (run-parametric-scenario, run-profiling-scenario...) are presents
• [ ] 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