Move version.py file to align with the PTB standard

[ArBridgeman]

Currently, the version.py file is in <root>/version.py, but the convention for projects using the PTB is for it to be <root>/exasol/transformers_extension/version.py. In order to accommodate this unique structure, the version_filepath in the BaseConfig has been overridden in the noxconfig.py file.

Important Notes

• This can only be done after Change directory structure for source_code to align with the PTB standard #80 .
• There is an ongoing request in the PTB if a version.py file is truly needed -> Check if can remove version.py python-toolbox#629. So depending on when this is done, it might be that this change is no longer relevant.

Tasks

• Change where version.py is saved
• Update the noxconfig.py
• Check & alter any CI pipelines
• Check & alter the pyproject.toml
• Check & alter any documentation