Refactor SerialManager to dynamic drivers + transport; add identify() and fix logger duplication

[MarkoVcode]

Summary

• Refactor SerialManager to dynamically load devices from config.yaml and instantiate driver classes via dynamic import
• Introduce shared SerialTransport abstraction to handle serial settings and EOLs
• Update existing drivers (owon_oel, owon_spm, owon_xdm, tenma_psu) to use the transport and implement identify() issuing *IDN?
• Fix logger duplication by preventing duplicate handlers and disabling propagation
• Add tests that mock pyserial via transport to validate identify() and SerialManager behavior

Changes

• benchmesh-serial-service/src/benchmesh_service/transport.py (new): SerialTransport, parse_serial_mode
• benchmesh-serial-service/src/benchmesh_service/serial_manager.py: dynamic driver import, manifest EOL injection, config.yaml loading
• benchmesh-serial-service/src/benchmesh_service/drivers/owon_oel.py: use transport, implement identify()
• benchmesh-serial-service/src/benchmesh_service/drivers/owon_spm.py: use transport, implement identify()
• benchmesh-serial-service/src/benchmesh_service/drivers/owon_xdm.py: use transport, implement identify()
• benchmesh-serial-service/src/benchmesh_service/drivers/tenma_psu.py: use transport, implement identify()
• benchmesh-serial-service/src/benchmesh_service/logger.py: avoid duplicate handlers, disable propagation
• benchmesh-serial-service/tests/test_driver_identify.py (new): tests identify() per driver
• benchmesh-serial-service/tests/test_serial_manager.py: updated to mock transport-level serial

Testing

• All tests pass locally: pytest -q benchmesh-serial-service/tests

Notes

• No changes to manifests or config.yaml.
• TENMA driver uses manifest alias tenma_psu -> tenma_72 for manifest lookup.

Co-authored-by: openhands openhands@all-hands.dev