Ignore known but unimplemented sat systems when reading RINEX3

[peci1]

RINEX3 file https://igs.bkg.bund.de/root_ftp/IGS/BRDC/2024/124/BRDC00WRD_R_20241240000_01D_MN.rnx.gz contains Geosync satellite NAV messages which are not fully implemented in GNSSTk. When reading the data with RinexNavDataFactory, the reading immediately fails on the first Geosync satellite and makes it impossible to import the rest of the file.

This PR makes GNSSTk ignore these records instead of failing on them.

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Reproducer:

gnsstk::NavLibrary lib;
gnsstk::NavDataFactoryPtr fac = std::make_shared<gnsstk::RinexNavDataFactory>();
fac->addDataSource(std::string(TEST_CACHE_DIR) + "BRDC00WRD_R_20241240000_01D_MN.rnx");
lib.addFactory(fac);
std::cout << gnsstk::printTime(gnsstk::CivilTime(lib.getInitialTime()), "%Y-%m-%d %H:%M:%f") << " --- "
          << gnsstk::printTime(gnsstk::CivilTime(lib.getFinalTime()), "%Y-%m-%d %H:%M:%f") << std::endl;

Output without this PR:

4713-1-1 0:0:0.000000 --- -4713-1-1 0:0:0.000000

Output with this PR:

2024-5-2 22:0:0.000000 --- 2024-5-4 0:25:0.000000