0.2.0a5

Major refactor:

• Dropped flit_core dependency
• Removed support for cross.copy_from_native_build option: when cross-compilation requires a native build, it is recommended to carry this out manually beforehand (e.g. using the py-build-cmake CLI).
• Renamed cmake.python_extension_abi option to python_abi.
• Added --loglevel (PY_BUILD_CMAKE_LOGLEVEL) flag/environment variable.
• Improved tests
• Improved logging for GitHub Actions
• PyPI trusted publishing

Full Changelog: 0.2.0a4...0.2.0a5