feat: Implement EIV linear detrending based on Kelly (2007) (sampling is ok,...

feat: Implement EIV linear detrending based on Kelly (2007) (sampling is ok, reporting is still a little bugged)

- Added `parse_eiv_linear` function to parse EIV linear detrending configurations.
- Integrated EIV components into the NumPyro model, including computation of mean shift and variance inflation.
- Added validation for EIV columns in the data loader.
- Created a new module `eiv.py` for EIV-related computations.
- Updated configuration generator and documentation to include EIV linear detrending options.
- Added unit tests for EIV functionality, covering both mathematical computations and configuration parsing.