Add CTest fixtures for parallel testing

[bobpaw]

This except from a failing run shows that ctest DEPENDS is simply not good enough -- the dependent test started after its requirement, but before the first test had completed! Fixtures are therefore required for parallel testing.

      Start 31: gmshV4AirFoil
28/55 Test #30: gmshv2TwoQuads ...................   Passed    0.21 sec
      Start 32: gmshV4AirFoil_dmgDiff
29/55 Test #32: gmshV4AirFoil_dmgDiff ............***Failed    0.00 sec
/usr/bin/diff: /home/runner/work/core/core/pumi-meshes/gmsh/v4/AirfoilDemo.dmg: No such file or directory

      Start 33: verify_serial
30/55 Test #33: verify_serial ....................   Passed    0.22 sec
      Start 34: verify_2nd_order_shape_quads
31/55 Test #27: create_misCube ...................   Passed    0.57 sec
      Start 35: verify_2nd_order_shape_tris
32/55 Test #34: verify_2nd_order_shape_quads .....   Passed    0.21 sec
      Start 36: uniform_serial
33/55 Test #35: verify_2nd_order_shape_tris ......   Passed    0.20 sec
      Start 37: classifyThenAdapt
34/55 Test #37: classifyThenAdapt ................   Passed    0.21 sec
      Start 38: tet_serial
35/55 Test #38: tet_serial .......................   Passed    0.29 sec
      Start 39: applyMatrixFunc
36/55 Test #36: uniform_serial ...................   Passed    0.53 sec
      Start 40: outputcontrol
37/55 Test #39: applyMatrixFunc ..................   Passed    0.21 sec
      Start 41: parmaSerial
38/55 Test #31: gmshV4AirFoil ....................   Passed    1.28 sec

Originally posted by @bobpaw in https://github.com/SCOREC/core/issues/500#issuecomment-2997696848