Re-estructure to enable packaging of the tool + convetional test structure

[gastmaier]

As is, the scripts are invoked by path, being brittle for CI/CD usage
and inconvenient for local usage. Add a basic pyproject.toml to enable

pip install git+https://github.com/TNG/KernelSbom

And future pypi deployment. The invocation changes to

SRCARCH=... kernel-sbom ...

a wrapper like

"""
Entry point for backwards compatibility.
"""

from kernel_sbom.__main__ import main

if __name__ == "__main__":
    main()
	
	

is not tried because requires kernel_sbom installed as a package, so still breaks the CI/CD of any users of the package anyway.

Also restructure the tests for a pythonic tests/ folder structure.

[augelu-tng]

Thanks for your ideas.

Our main goal is to contribute this project to the mainline Linux kernel repository. For that, we need to be able to map the sbom directory directly into linux/scripts/sbom (see for example augelu-tng/linux#3). We do want to contribute the unit tests but no integration tests which is why we keep integration tests outside of the sbom directory.

Can you update the PR to not conflict with these requirements ?