C内核流量计算方法优化，前端文件名称读取优化

tests/test_native_only_backend.py

@@ -29,7 +29,7 @@ sys.meta_path.insert(0, NoNumericalPython())
 from app.main import compile_system_xml_network
 from app.simulation.native_codegen.compiler import compile_native_program
 from app.system_xml import validate_system_xml_document
-doc = validate_system_xml_document(Path('tests/data/native-skill-test.xml').read_bytes()).document
+doc = validate_system_xml_document(Path('tests/fixtures/native-skill-test.xml').read_bytes()).document
 program = compile_native_program(compile_system_xml_network(doc))
 assert len(program.state_keys) == 12
 assert len(program.variables) == 175