The `USE_EXPERIMENTAL_TESTS` variable was not exposed as an option, so the two tests that use the option to check whether tests should be run had to be manually enabled by changing `tests/python/CMakeLists.txt`. This commit renames the variable to `WITH_TESTS_EXPERIMENTAL`, defaults the option to `OFF`, and marks it as an advanced option. Pull Request: https://projects.blender.org/blender/blender/pulls/133831