POC: Unit tests in Github Actions

[TonyCTHsu]

What does this PR do?

This is a POC to run Unit tests in Github Actions. The same strategy using dynamic matrix has already been adopted at our CI gem: DataDog/datadog-ci-rb#258

The UI looks like: https://github.com/DataDog/datadog-ci-rb/actions/runs/12050920794

I have only enable two ruby versions and execute on specific events because it is still unfinished with some scalability/reliability blockers to be done in the future:

• Matrix per workflow to 256 jobs
• Rate limit from Dockerhub, tracked: Publish images for service container images-rb#15

This should be influence other workflow and should not be required check before we are fully committed.

[datadog-datadog-prod-us1]

Datadog Report

Branch report: poc/circle-to-gha
Commit report: a40a8e9
Test service: dd-trace-rb

✅ 0 Failed, 22038 Passed, 1459 Skipped, 5m 37.26s Total Time

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-12-03 10:50:53

Comparing candidate commit a40a8e9 in PR branch poc/circle-to-gha with baseline commit 646d17a in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.