Update the GCOV workflow to use the native Doppler to compute the platform position for RTC

[gshiroma]

This PR updates the GCOV workflow to use the native Doppler to compute the platform position for RTC. The updated platform position is used to compute the local incidence angle and incidence angle, which are used to compute the RTC normalization factors. This PR also exposes the option of using the zero-Doppler or native Doppler LUTs for grid and platform position in the GCOV runconfig.