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

Summary

Recently, GEOS's version in Debian's repositories was updated to 3.9.0. This new version brings some minor updates to the algorithms that slightly changes the results of the segmentation in OTB. This changes are so small that the symmetrical difference in QGIS doesn't detect them. But they make the CI fail. To fix this (and to be homogeneous across all the platforms), it would be best to update this dependency in the SuperBuild. But OSSIM is not compatible with GEOS 3.9.0, so we need to wait until ossim is removed. The chosen solution is to add a new baseline especially for Debian.

The version of openCV was updated too, to 4.5.1. It also changes the results of the classification in OTB (see 1 and 2). Even though the models are slightly different, the result is either as good or better. So we can safely update the version of openCV in the SuperBuild and the baseline.

Rationale

Closes #2197 (closed)

Implementation Details

Classes and files

• Set the new version of openCV in SuperBuild/CMake/External_opencv.cmake.

Tests

• Add a new baseline with the new values obtained with GEOS 3.9.0
• Update the baseline for openCV 4.5.1

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement
• Optionally, run git diff develop... -U0 --no-color | clang-format-diff.py -p1 -i on latest changes and commit