test(lib-injection): test telemetry (#9477)

[gnufede]

This change adds automated testing of the instrumentation telemetry emitted by the library injection workflow. It takes the approach of setting DD_TELEMETRY_FORWARDER_PATH to point to a simple bash script that writes to a file, then checking the contents of that file against per-test expectations about specific telemetry events.

I am planning on adding the following data to telemetry events emitted by ddtrace itself in a separate pull request:

• whether autoinjection was used

• whether the force envvar was set

• whether autoinjection actually installed anything

• [x] Change(s) are motivated and described in the PR description

• [x] Testing strategy is described if automated tests are not included in the PR

• [x] Risks are described (performance impact, potential for breakage, maintainability)

• [x] Change is maintainable (easy to change, telemetry, documentation)

• [x] Library release note guidelines are followed or label changelog/no-changelog is set

• [x] Documentation is included (in-code, generated user docs, public corp docs)

• [x] Backport labels are set (if applicable)

• [x] If this PR changes the public interface, I've notified @DataDog/apm-tees.

---

Co-authored-by: ZStriker19 zach.groves@datadoghq.com Co-authored-by: Zachary Groves 32471391+ZStriker19@users.noreply.github.com (cherry picked from commit ea13466504338b54550827371068a54fd5a7721a)

Checklist

• [ ] Change(s) are motivated and described in the PR description
• [ ] Testing strategy is described if automated tests are not included in the PR
• [ ] Risks are described (performance impact, potential for breakage, maintainability)
• [ ] Change is maintainable (easy to change, telemetry, documentation)
• [ ] Library release note guidelines are followed or label changelog/no-changelog is set
• [ ] Documentation is included (in-code, generated user docs, public corp docs)
• [ ] Backport labels are set (if applicable)
• [ ] If this PR changes the public interface, I've notified @DataDog/apm-tees.

Reviewer Checklist

• [ ] Title is accurate
• [ ] All changes are related to the pull request's stated goal
• [ ] Description motivates each change
• [ ] Avoids breaking API changes
• [ ] Testing strategy adequately addresses listed risks
• [ ] Change is maintainable (easy to change, telemetry, documentation)
• [ ] Release note makes sense to a user of the library
• [ ] Author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
• [ ] Backport labels are set in a manner that is consistent with the release branch maintenance policy