WIP: Replace "vnl_sample.h" with <random> in ConnectedComponent tests

[N-Dekker]

• Another follow-up to pull request ENH: Replace "vnl/vnl_sample.h" with <random>, in Core tests #5611

[dzenanz]

Looks good on a glance.

[N-Dekker]

• The first of the two commits (on ConnectedComponent tests) has test failures that I find hard to fix. So I branched off the other one (on Voronoi), which should be easier to get passed: pull request ENH: Replace "vnl_sample.h" with <random> in VoronoiSegmentation tests #5624

[N-Dekker]

There appeared test failures at https://open.cdash.org/viewTest.php?onlyfailed&buildid=10817138 on the following four tests:

1. itkConnectedComponentImageFilterTest
2. itkConnectedComponentImageFilterTest2
3. itkConnectedComponentImageFilterTest3
4. itkConnectedComponentImageFilterTestRGB

I'm sorry, I don't really know how to fix them, but I guess we would have to change the ground truth images (somewhere in ${ITK_DATA_ROOT}, in order to make this work. For example, for itkConnectedComponentImageFilterTestRGB:

ITK/Modules/Segmentation/ConnectedComponents/test/CMakeLists.txt

Lines 44 to 55 in 6568876

	itk_add_test(
	NAME itkConnectedComponentImageFilterTestRGB
	COMMAND
	ITKConnectedComponentsTestDriver
	--compare
	DATA{${ITK_DATA_ROOT}/Baseline/BasicFilters/ConnectedComponentImageFilterTest.png,:}
	${ITK_TEST_OUTPUT_DIR}/ConnectedComponentImageFilterTestRGB.png
	itkConnectedComponentImageFilterTestRGB
	DATA{${ITK_DATA_ROOT}/Input/cthead1.png}
	${ITK_TEST_OUTPUT_DIR}/ConnectedComponentImageFilterTestRGB.png
	130
	145

Does anyone have suggestion?