Migrate all code from flat accessor pattern (options.tesseract_timeout)
to the plugin namespace pattern (options.tesseract.timeout).
Key changes:
- Fix _get_plugin_options to raise AttributeError for unregistered
namespaces instead of silently returning None
- Add _convert_value helper to convert PathLike to str for plugin
model field compatibility
- Filter out _plugin_cache_* entries from JSON serialization to fix
worker process serialization (test_simulate_oom_killer)
- Update tesseract_ocr.py, ghostscript.py, _validation_coordinator.py,
and _pipelines/ocr.py to use options.tesseract.* and
options.ghostscript.* accessors
- Update tests to use setup_plugin_infrastructure() for plugin
model registration
James R. Barlow
9ebba91466