Add test case for Uvicorn log format

This commit will add a pytest parameter that verifies log message output
after configuring logging with the Uvicorn log format. This parameter is
important for testing not only for the log message format, but also the
use of the `uvicorn.logging.DefaultFormatter` class and its module. The
module has been renamed from `uvicorn.logging` to `uvicorn._logging`,
then reverted back to `uvicorn.logging`. The test will help ensure that
the Uvicorn module path (`uvicorn.logging.DefaultFormatter`) is correct.

encode/uvicorn#1543

tests/test_logging_conf.py

@@ -160,7 +160,8 @@ def test_logging_output_default(self, capfd: pytest.CaptureFixture) -> None:
         assert "Hello, World!" in captured.out
 
     @pytest.mark.parametrize(
-        "log_format,log_level_output", (("gunicorn", "[DEBUG]"), ("verbose", "DEBUG"))
+        "log_format,log_level_output",
+        (("gunicorn", "[DEBUG]"), ("uvicorn", "DEBUG: "), ("verbose", "DEBUG  ")),
     )
     def test_logging_output_custom_format(
         self,
@@ -172,7 +173,7 @@ def test_logging_output_custom_format(
     ) -> None:
         """Test logger output with custom format."""
         logging_conf_file = f"{logging_conf_tmp_file_path}/tmp_log.py"
-        monkeypatch.setenv("LOG_FORMAT", "gunicorn")
+        monkeypatch.setenv("LOG_FORMAT", log_format)
         monkeypatch.setenv("LOG_LEVEL", "debug")
         logger = logging_conf.logging.getLogger()
         logging_conf.configure_logging(logging_conf=logging_conf_file)