chore: use separate directory for testrunner container riot

[romainkomorndatadog]

Small quality-of-life improvement to separate the .riot directory used when inside a testrunner container from the .riot directory outside the container. This is achieved simply by changing the bind-mounted directory when the container is started with docker-compose.

This is primarily because the testrunner's riot envs will have symlinks to Python binaries in /root/ which are incorrect outside of the container.

This makes it less likely that there would be issues when developers mix running tests inside the container with using workflow-related riot commands outside of the container.

Two notable locations where .riot remains untouched:

• scripts/compile-and-prune-test-requirements: this needs to run outside of the container in order to modify the proper files
• scripts/run-test-suite: this would either run outside or inside the container (although I don't think anyone uses it manually anyway since it requires a bit of setup)

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

[datadog-dd-trace-py-rkomorn]

Datadog Report

Branch report: romain.komorn/chore/use_container_specific_riot
Commit report: bc665fc
Test service: dd-trace-py

✅ 0 Failed, 51932 Passed, 82 Skipped, 6h 28m 31.62s Total duration (11m 2.87s time saved)
⌛ 1 Performance Regression

⌛ Performance Regressions vs Default Branch (1)

• test_export_reset - test_http.py 5.7s (+4.66s, +447%) - Details

[romainkomorndatadog]

I'm abandoning this in favor of just setting a different riot env path in my .zshrc .