TEST: take into account that deburst functions return false in SarSensorModel (GRD and 1 burst SLC products)

REFAC: make otb::SarSensorModel independant of otb::ImageMetadata and use MJD stored as double (adapted from ossim plugins) instead of boost datetime (which has insufficient microsecond precision by default)

ENH: Update openCV version to 4.5.1 for the SuperBuild, update the baseline for GEOS

Closes #2197

See merge request !822

Update EXPAT to version 2.4.1

See merge request !821

apTvSeSegmentationCCVector_ULOVW, apTvSeSegmentationCCVector_ULU and
apTvSeSegmentationMeanshiftVector

Those tests don't pass with GEOS version 3.9.0.