Tests: Move sculpting render tests out of WITH_GPU_RENDER_TESTS

Adds a new CMake option so that these tests can be run independently of
other tests, and so that existing tests that use WITH_GPU_RENDER_TESTS
are not forced to run these sculpt tests.

Pull Request: https://projects.blender.org/blender/blender/pulls/134893

tests/python/CMakeLists.txt

@@ -1192,7 +1192,7 @@ endif()
 # ------------------------------------------------------------------------------
 # SCULPTING RENDER TESTS
 
-if(WITH_GPU_RENDER_TESTS)
+if(WITH_GPU_MESH_PAINT_TESTS)
   if(NOT OPENIMAGEIO_TOOL)
     message(STATUS "Disabling sculpting render tests because OIIO oiiotool does not exist")
   else()