Add the ResInsight-featuretests executable: a headless GUI test harness (RiaFeatureTestModelBuilder, RiaFeatureTestTreeView), a runner that triggers Ric*Feature commands through their QAction (RicFeatureExecutionRunner), a generic execution sweep over every registered feature (RicFeatureSweep-Test, RicFeatureExecutionSweep-Test, RicFeatureSubprocessSweep-Test, RicFeatureSweepDenylist), and supporting CMake wiring. Adds RiaRegressionTestRunner::setRunningRegressionTests() so tests can suppress modal dialogs, and shares RimMockSummaryCase as a common test model under TestModels.
