refactor: consolidate config and env records into SaveRecord with SaveType (#1656)

* Clarify client description against backend API

* Consolidate config and env records into SaveRecord with SaveType

* test: adapt tests to SaveRecord consolidation, make group_records_by_type resilient to unknown types

- Update all test imports from deleted config/env proto modules to SaveRecord/SaveType
- Replace ConfigRecord/UpdateType usages in test fixtures with SaveRecord(type=SAVE_TYPE_CONFIG)
- Adjust test assertions: event.update → event.path, oneof group keys config → save
- Adapt consumer flush recovery test to use _log_batch instead of removed _config_batch
- Remove deleted oneof fields (config/metadata/requirements/conda) from record_kind helpers
- Wrap group_records_by_type ValueError in safe.block to gracefully skip unrecognized record types

* Fix typo in SAVE_TYPE_METADATA enum value

* chore: remove redundant Path() wrapping in sender.py open() calls