Add Open Babel Rex module support

[UMI5751]

Summary

• add Open Babel protonation wrapper with raw-config Rex support
• update module lock for staging openbabel_openbabel_protonate_rex
• add onboarding test and docs entry

Testing

• python -m compileall -q src/rush
• timeout 1200s python -m pytest -q tests/test_onboarding_openbabel.py

Notes

• module repo: https://github.com/talo/openbabel_rex @ 9f75cf354e62561f15bfa0d7728f52f7b0812f01
• module keys: openbabel_openbabel_protonate_rex