Fix pspm_convert_ppg2hb HeartPy handling and extend test coverage

[4gwe]

Fixes #597 and #652.

Changes proposed in this pull request:

• Improved pspm_convert_hb2hp test coverage (Test function for convert_hb2hp #597).
• Fixed HeartPy input handling in pspm_convert_ppg2hb.
• Filtered out peaks rejected by HeartPy using binary_peaklist.
• Improved HeartPy error handling.
• Fixed LSM edge cases and option validation.
• Added tests for HeartPy, rejected peaks, channel selection, invalid options, and LSM behavior.
• Added HeartPy to the GitHub Actions dependencies.