Add test cases and .gitignore

This adds test cases from the pmbootstrap repository, and adjusts them to work with the new pmaports repository. Created an early WIP version, so the scripts can be tested with gitlab's CI.

TODO:

• rework test_aportgen.py (move it to pmbootstrap, use static input and output files for checking - version check is already done in test_upstream_compatibility.py)
• update GPL header (still says this is part of "pmbootstrap") - go with the short SPDX header instead
• add license header in every file
• adjust paths in static code analysis script
• make CI go through
• good commit message