Merge topic 'ctest-j-default' into release-3.29

5de1e21659 ctest: Allow passing -j without value to choose a contextual default
bbcbcff7d9 cmCTestMultiProcessHandler: Modernize member initialization
7457b474a1 Tests: Remove unnecessary parallel suppression from CTestCoverageCollectGCOV
ae69801d96 Tests: Convert CTestTestSkipReturnCode to RunCMake.ctest_test case
30dda49416 Tests: Convert CTestTestSerialOrder to RunCMake.ctest_test case

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Acked-by: scivision <michael@scivision.dev>
Merge-request: !9315