PyJobTransformsCore: delete majority of legacy transform code
The only remaining use-cases are:
EvgenJobTransforms
- the standalone command line utilities
find_data.py
,find_library.py
andfind_python_modules.py
Once these are removed we can delete the entire package.
Doing this in main since other cleanups (e.g. AthFile) have happened in the meantime to this obsolete code that would cause conflicts.