Feat!: Major changes to support multi-architecture builds

[ModeSevenIndustrialSolutions]

• Added auditwheel repair step to support multiplatform wheel files
• Added auditwheel and manylinux_version inputs
• Add build_formats input: wheel, sdist, or both (default: both)
• build_formats input allows sdist builds to be broken off separately
• Replace python-project-metadata-action with build-metadata-action

The build_formats input allows sdist builds to be separated from wheel files, as otherwise they end up in multi-architecture matrix jobs, creating overlapping build artefacts that then fail to upload/attach to the workflow run due to naming conflicts. The new input allows more fine-grained control in the calling workflow, by not baking an assumption into the build action itself.

Added PYTHON_TEST_PROJECTS JSON variable to the repo, and modified the testing.yaml workflow to use it, so we now build a wider selection of RelEng Python projects in parallel as a matrix job. This should pickup problems earlier when making changes to the action that cause breakage.

[Copilot]

Pull request overview

This PR introduces comprehensive multi-architecture build support for Python projects by adding auditwheel wheel repair capabilities, flexible build format control, and improved metadata handling. The changes enable building platform-specific wheels (x86_64, aarch64) with proper manylinux tags for PyPI distribution while preventing artifact naming conflicts in matrix builds.

Key Changes

• Multi-architecture wheel support: Added auditwheel and manylinux_version inputs to repair wheels with proper manylinux platform tags (manylinux_2_34 default) for PyPI compatibility
• Build format control: New build_formats input (wheel/sdist/both) allows separating wheel and sdist builds across different matrix jobs to avoid artifact conflicts
• Enhanced metadata handling: Replaced python-project-metadata-action with build-metadata-action, added artefact_name input for custom artifact naming, and python_version input for build version override
• Improved robustness: Migrated from environment variables to direct input interpolation, added set -euo pipefail to all bash scripts, and enhanced cache clearing with better error handling
• Expanded testing: Added matrix-based testing across multiple Python projects using repository variables, including dedicated multi-architecture test jobs

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
docs/MANYLINUX_CONFIG.md	New comprehensive documentation for manylinux configuration, auditwheel usage, platform tags, and multi-architecture build examples
action.yaml	Core changes: added 5 new inputs (artefact_name, python_version, build_formats, auditwheel, manylinux_version), replaced metadata action, implemented auditwheel wheel repair step, updated SigStore signing to respect build_formats, migrated to direct input interpolation
README.md	Updated with multi-architecture examples, new input parameters documentation, clearer versioning strategy explanations, and expanded permissions documentation
.github/workflows/testing.yaml	Enhanced testing with two new matrix jobs: test-python-projects (using TEST_PROJECTS variable) and test-multi-arch-projects (testing x86_64 and aarch64 builds)

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