feat: update respiration validation and ECG feature dependency

• Update ecg_feature_extraction dependency to the latest commit
• Enable GoogleTest coverage integration unconditionally
• Build and register GoogleTest targets without feature gating
• Update zero-crossing respiration estimation to use latest 8 intervals
• Expand supported respiration period and rate range
• Add respiration rate validation for BIDMC01 dataset
• Generate derived respiration and rate comparison CSV data
• Reduce debug logging in respiration and validation tests
• Update zero-crossing respiration test naming and signal duration
• Clean up loop formatting and test runner configuration