feat!: drop support for end-of-life python versions

[jkowalleck]

currently, we support python >= 3.8

this means, we do support python versions that are end-of-life. see https://devguide.python.org/versions/

• py38 - EOL 2024-10-07
• ... TBC ...

proposal

• drop support for EOL py-versions
• raise the min-version of supported python to the latest feature-release of a reasonable new py-version
• migrate code and tooling to new min-version

[jkowalleck]

released via https://github.com/CycloneDX/cyclonedx-python/releases/tag/v6.0.0