Draft: Set Default SSIM Threshold according to doc

This leads to false positive...

This test output

does not fail against this baseline...

Note the threshold value in ctest output:

711: Test command: /home/nicolas/ParaView/branch1/build/bin/vtkInteractionWidgetsCxxTests "TestImplicitAnnulusWidget" "-D" "/home/nicolas/ParaView/branch1/build/ExternalData/VTK/Testing" "-T" "/home/nicolas/ParaView/branch1/build/Testing/Temporary" "-V" "/home/nicolas/ParaView/branch1/build/ExternalData/VTK/Interaction/Widgets/Testing/Data/Baseline/TestImplicitAnnulusWidget.png"
711: Working Directory: /home/nicolas/ParaView/branch1/build/VTK/Interaction/Widgets/Testing/Cxx
711: Environment variables: 
711:  VTK_TESTING=1
711:  VTK_TESTING_IMAGE_COMPARE_METHOD=TIGHT_VALID
711: Test timeout computed to be: 1500
711: (   2.167s) [main thread     ]         vtkTesting.cxx:739   INFO| Using TIGHT_VALID image comparison method.
711: (   2.168s) [main thread     ]         vtkTesting.cxx:808   INFO| Comparing baselines using the default image baseline.
711: (   2.899s) [main thread     ]         vtkTesting.cxx:775   INFO| When comparing images, error is defined as the maximum of all individual values within the used method (TIGHT or LOOSE) using the threshold 10
711: (   2.899s) [main thread     ]         vtkTesting.cxx:778   INFO| Error computations on Lab channels using Minkownski and Wasserstein distances:
711: (   2.899s) [main thread     ]         vtkTesting.cxx:780   INFO| TIGHT_VALID metric (euclidian): 0.460778
711: (   2.899s) [main thread     ]         vtkTesting.cxx:781   INFO| LOOSE_VALID metric (manhattan / earth's mover): 0.272567
711: (   2.899s) [main thread     ]         vtkTesting.cxx:782   INFO| Note: if the test fails but is visually acceptable, one can make the test pass by changing the method (TIGHT_VALID vs LOOSE_VALID) and the threshold in CMake.
711: <DartMeasurement name="ImageError" type="numeric/double">0.460778</DartMeasurement><DartMeasurement name="BaselineImage" type="text/string">Standard</DartMeasurement><DartMeasurement name="WallTime" type="numeric/double">0.747711</DartMeasurement>
711: <DartMeasurement name="CPUTime" type="numeric/double">10.8296</DartMeasurement>
1/1 Test #711: VTK::InteractionWidgetsCxx-TestImplicitAnnulusWidget ...   Passed    3.00 sec

The following tests passed:
	VTK::InteractionWidgetsCxx-TestImplicitAnnulusWidget

Test: https://gitlab.kitware.com/vtk/vtk/-/blob/master/Interaction/Widgets/Testing/Cxx/TestImplicitAnnulusWidget.cxx?ref_type=heads CMakeLists does not do anything special: https://gitlab.kitware.com/vtk/vtk/-/blob/master/Interaction/Widgets/Testing/Cxx/CMakeLists.txt?ref_type=heads