Remove designator aggregate intialization so code compiles with C++17

.gitlab-ci.yml

src/csg/tests/levelset/boolean.t.cpp

src/csg/tests/levelset/empty.t.cpp

src/csg/tests/levelset/extrude.t.cpp

src/csg/tests/levelset/internal_flow.t.cpp

src/csg/tests/levelset/primitives.t.cpp

src/csg/tests/levelset/transform.t.cpp