Enhancements for EM Counterpart Detection and Bandpass Interpolation (sncosmo)

[weizmannk]

This pull request is designed to address and introduce certain processes:

1. Bilby Integration with gpstime:

   • The process now utilizes gpstime provided in the injections.dat file for enhanced accuracy.

2. Integration of snscosmo _BANDPASS_INTERPOLATORS:

   • Added functionality to retrieve bandpass interpolators, with support for the 'ultrasat' filter. This enhancement extends the capabilities of our bandpass interpolation.

3. Revamp of EM Counterpart Detection in gwemopt:

   • The detection process for Electromagnetic (EM) counterparts has been restructured. This update is focused on incorporating a range of telescopes including ULTRASAT, LSST, ZTF, and others specified in the gwemopt config file.
   • Default proxy filters are set as follows:
     • 'ultrasat' band for ULTRASAT (noting that 'ultrasat' is the only filter of ULTRASAT )
     • 'ps1__r' band for LSST.
     • 'ztfr' band for ZTF.
   • For telescopes other than ULTRASAT, LSST, and ZTF, users are required to specify the proxy band.

[mcoughlin]

LGTM