Use sysconfig.get_platform() to determine each interpreter's CPU architecture (arm64, x86_64, etc.) and expose it via a new 'machine' property on PythonInfo and an optional machine suffix on PythonSpec.

This allows users to distinguish between interpreters that share the same version and bitness but target different architectures, e.g.: virtualenv --python cpython3.12-64-arm64 .venv

Thanks for contributing, make sure you address all the checklists (for details on how see development documentation)

Refs: #3069"

• ran the linter to address style issues (tox -e fix)
• wrote descriptive pull request text
• ensured there are test(s) validating the fix
• added news fragment in docs/changelog folder
• updated/extended the documentation