feat(tests): add comprehensive end-to-end integration tests for ReadFrom configuration

- Add ReadFromEndToEndIntegrationTests with 48 test cases covering complete pipeline
- Test connection string to FFI layer flow for all ReadFromStrategy values
- Test ConfigurationOptions programmatic configuration flow
- Test error handling throughout the complete configuration pipeline
- Test round-trip serialization (Parse → ToString → Parse) integrity
- Test backward compatibility with legacy configurations
- Test performance scenarios with concurrent connections
- Test FFI layer integration to verify configuration reaches Rust core
- Verify AZ affinity settings are properly passed to the Rust core
- Cover both standalone and cluster client scenarios
- Fix test case for invalid ReadFrom strategy to avoid parsing ambiguity

Implements task 12 from AZ Affinity support implementation plan.
Requirements covered: 3.1, 3.2, 3.3, 3.4, 3.5

Signed-off-by: jbrinkman <[email protected]>

Author: jbrinkman