Make ECG detection parameters configurable
- Add EcgFeaturesDetectionConfig for RR, QRS, P-wave, PTU, and T-wave parameters
- Replace hardcoded ECG detection thresholds and offsets with configuration values
- Add parameter validation before ECG feature and rhythm processing
- Make previous beat output offset configurable
- Improve QRS refractory period and RR interval validation
- Add configurable P-wave search and slope detection parameters
- Add configurable T-wave search, slope, and amplitude thresholds
- Correct raw ECG debug output format specifiers in validation tests
- Remove obsolete ECG processing and commented-out configuration code