Bug 2029522 - Modernize CI workflow: docker compose v2 and actions/checkout@v4

[loganrosen]

Updates the GitHub Actions CI workflow and Dockerfile to remove deprecated tooling:

• actions/checkout@v3 → v4 — v3 uses Node 16 which GitHub has deprecated
• Remove apt install docker-compose — GitHub Actions runners already include Docker Compose v2 as a plugin, so the install step is unnecessary overhead
• docker-compose → docker compose — the hyphenated v1 (Python-based) tool is deprecated in favor of the v2 Go plugin
• Remove CircleCI ARGs/ENVs from Dockerfile — CIRCLE_SHA1 and CIRCLE_BUILD_URL are unused since CI moved to GitHub Actions

Testing: This PR's own CI run validates the changes — the updated ci.yml on this branch is what GitHub Actions will execute. Compose v2 compatibility verified locally with docker compose -f docker-compose.test.yml config.

[dklawren]

This looks good so far and thanks for the help.

Two issues:

Please also update .github/workflows/deploy.yml to use the same cleanup actions where appropriate.

Also Dockerfile and extensions/BMO/Extension.pm use the CIRCLE_* variables to populate values in version.json in install_filesystem(). These will need to be update to use GITHUB_* equivalent variables and values.

For example in the Dockerfile:

  ARG GITHUB_SHA
  ARG GITHUB_SERVER_URL
  ARG GITHUB_RUN_ID

  ENV GITHUB_SHA=${GITHUB_SHA}
  ENV GITHUB_RUN_URL=${GITHUB_SERVER_URL}/mozilla-bteam/bmo/actions/runs/${GITHUB_RUN_ID}

And then update Extension.pm to read the new variable names.

[loganrosen]

@dklawren Addressed, thanks!

[dklawren]

Thanks!