[tes3] Further reorganize tests; revise some Py functional tests ()

Sample/HardParticle/Polyhedra.cpp

Sample/HardParticle/Polyhedra.h

Tests/Functional/CMakeLists.txt

Tests/Functional/LibFit/ClassicalTestFunctions.cpp

Tests/Functional/LibFit/ClassicalTestFunctions.h

Tests/Functional/LibFit/MinimizerTests.cpp

Tests/Functional/LibFit/PlanCases.cpp

Tests/Functional/LibFit/PlanCases.h

Tests/Functional/LibFit/ResidualTestPlan.cpp

Tests/Functional/LibFit/ResidualTestPlan.h

Tests/Functional/LibFit/ScalarTestPlan.cpp

Tests/Functional/LibFit/ScalarTestPlan.h

Tests/Py/CMakeLists.txt

Tests/Py/Embedded/README.md

Tests/Py/Fit/CMakeLists.txt

Tests/Py/Fit/minimizer_api.py

Tests/Py/Functional/CMakeLists.txt

Tests/Py/Functional/sliced_compounds.py

Tests/Py/Functional/sliced_spheres.py

Tests/Py/Functional/transform_BoxComposition.py