Allow subfolder for regression tests.

regression-tests/cpu/gyroidsrow_test.sh

regression-tests/cpu/laminar_pipe_flow_test.sh

regression-tests/cpu/laminar_plane_flow_test.sh

regression-tests/cpu/lid_driven_cavity_test.sh

regression-tests/gpu/actuator_line_test.sh

regression-tests/gpu/atmospheric_boundary_layer_test.sh

regression-tests/gpu/driven_cavity_test.sh

regression-tests/gpu/driven_cavity_uniform_test.sh

regression-tests/gpu/refined_sphere_in_channel_test.sh

regression-tests/gpu/sphere_in_channel_test.sh

utilities/ci-regression-tests/generate-ci.py

utilities/ci-regression-tests/regression-tests-ci.yml.j2