[RF] Move vectorised PDF tests from roottest to roofit

These useful tests are relatively short (runtime 28 seconds in total)
and test lower-level RooFit functionality.

Moving them from roottest to roofit has the following benefits:

 * Faster RooFit development experience: it's not necessary anymore to
   also add and compile all of `roottest`, if you want to make sure
   locally that the vectorized pdf tests always compile and pass.

 * The vectorized pdf tests will be able to consider the RooFit-internal
   preprocessor macros at build time, like `ROOFIT_CUDA` and
   `ROOFIT_LEGACY_EVAL_BACKEND`. Like this we can ensure that the tests
   will pass no matter how RooFit was configured at compile time. This
   is for me personally the strongest reason and was the motivator for
   this commit.

 * Avoid code repetition in `root` and `roottest`, because now the
   vectorized PDF tests will be able to re-use private code from RooFit.

 * If you want to build standalone RooFit with all tests, you won't have
   to stitch together the two repositories.

roofit/roofit/test/CMakeLists.txt

@@ -28,3 +28,5 @@ else()
   ROOT_EXECUTABLE(testRooFit testRooFit.cxx LIBRARIES RooFit)
   ROOT_ADD_TEST(test-fit-testRooFit COMMAND testRooFit)
 endif()
+
+add_subdirectory(vectorisedPDFs)

roofit/roofit/test/vectorisedPDFs/CMakeLists.txt

@@ -0,0 +1,67 @@
+if(CMAKE_CXX_COMPILER_ID STREQUAL Intel)
+  if(DEFINED ENV{VTUNE_AMPLIFIER_2019_DIR})
+    set(VTUNE_DIR ENV{VTUNE_AMPLIFIER_2019_DIR})
+  elseif(DEFINED ENV{VTUNE_PROFILER_2020_DIR})
+    set(VTUNE_DIR ENV{VTUNE_PROFILER_2020_DIR})
+  endif()
+  # To be able to start/stop the vtune profiler, ittnotify must be available.
+  target_include_directories(VectorisedPDFTests PUBLIC "${VTUNE_DIR}/include/")
+  target_link_libraries(VectorisedPDFTests INTERFACE "${VTUNE_DIR}/lib64/libittnotify.a")
+endif()
+
+add_library(VectorisedPDFTests STATIC VectorisedPDFTests.cxx)
+target_link_libraries(VectorisedPDFTests PUBLIC gtest ROOT::Gpad ROOT::RooFitCore ROOT::RooFit)
+
+ROOT_ADD_GTEST(testCompatMode testCompatMode.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testGauss testGauss.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testPoisson testPoisson.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testAddPdf testAddPdf.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testExponential testExponential.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testNestedPDFs testNestedPDFs.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testProductPdf testProductPdf.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testJohnson testJohnson.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testLandau testLandau.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testBukin testBukin.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testChebychev testChebychev.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testPolynomial testPolynomial.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testBernstein testBernstein.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testArgusBG testArgusBG.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testBifurGauss testBifurGauss.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testBreitWigner testBreitWigner.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testCBShape testCBShape.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testGamma testGamma.cxx
+              LIBRARIES VectorisedPDFTests)
+if(ROOT_mathmore_FOUND)
+  ROOT_ADD_GTEST(testLegendre testLegendre.cxx
+                LIBRARIES VectorisedPDFTests ROOT::RooFitMore)
+endif()
+ROOT_ADD_GTEST(testChiSquarePdf testChiSquarePdf.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testDstD0BG testDstD0BG.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testLognormal testLognormal.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testNovosibirsk testNovosibirsk.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testVoigtian testVoigtian.cxx
+              LIBRARIES VectorisedPDFTests)
+ROOT_ADD_GTEST(testGaussBinned testGaussBinned.cxx
+              LIBRARIES ROOT::Gpad ROOT::RooFitCore ROOT::RooFit)
+