BUILD-8099 build Poetry action

[julien-carsique-sonarsource]

• BUILD-8099 build poetry action
  • implement as a build action the Poetry build (regular_poetry_build_publish) from ci-common-scripts; see https://github.com/SonarSource/ci-common-scripts/pull/71
  • no need to restrict mise cache thanks to .github/workflows/pr-cleanup.yml
  • add ShellSpec tests
  • use mise.local.toml per action to not conflict with the caller mise.toml definition
• Build number cleanup
  • remove unused input run-id
  • add .sh file extension to the Shell script
• BUILD-8291 fix PR cleanup test
  • no execution on PR close for .github/workflows/test-pr-cleanup.yml
  • use actions/cache/save in .github/workflows/test-pr-cleanup.yml, no need for restore included in actions/cache
• BUILD-8099 100% shellspec coverage, including for pr_cleanup action
  • extract embedded Go templates to files, for readability and to circumvent a kcov issue (this was considered as uncovered code)
  • ShellSpec for the three actions, targeting 100% code coverage without testing unlikely corner and exotic cases
  • Run SonarCloud Code Analysis after unit tests
• Documentation
  • Fix Markdown lint to allow "Multiple headings with the same content" in different siblings
  • add CONTRIBUTE.md (inspired from ci-common-scripts) to describe action development and testing
• mise: add ShellSpec and JFrog CLI

Leftover draft code, comments and not implemented features (following PRs):

• improve setup of kcov, if possible (Debian package download and install at the moment)
• improve setup and usage of sonar-scanner-cli (ZIP package download and install at the moment)
• public build should use sonarsource-pypi-public (not available at the moment), instead of sonarsource-pypi
• set_build_env() function is very similar to source github-env <BUILD|BUILD-PRIVATE> used for Maven build: is there a path to factorization?
• as discussed, get-build-number is not called by the build-poetry action, it is expected to be provided by the caller. See https://github.com/SonarSource/sonar-dummy-python-oss/pull/38/files#diff-5c3fa597431eda03ac3339ae6bf7f05e1a50d6fc7333679ec38e21b337cb6721R29-R30 ; the alternative is kept in comments until we figure out what it the best user experience
• promotion

Tested with

• https://github.com/SonarSource/sonar-dummy/pull/439
• BUILD-8099 migration to GitHub Actions sonar-dummy-python-oss#38 (https://github.com/SonarSource/sonar-dummy-python-oss/actions/runs/15995072710/job/45116529655?pr=38)

[sonarqubecloud]

Please retry analysis of this Pull-Request directly on SonarQube Cloud

[matemoln]

Could you remove the ### Environment Variables section from the README?

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud