Update test runner to use PluginLogger (flutter#8535)

Part of flutter#8369

Author: helin24

src/io/flutter/run/test/FlutterTestRunner.java

@@ -31,6 +31,7 @@
 import com.jetbrains.lang.dart.util.DartUrlResolver;
 import io.flutter.FlutterUtils;
 import io.flutter.ObservatoryConnector;
+import io.flutter.logging.PluginLogger;
 import io.flutter.run.FlutterPositionMapper;
 import io.flutter.run.common.CommonTestConfigUtils;
 import io.flutter.sdk.FlutterSdk;
@@ -293,7 +294,7 @@ private void dispatchJson(String json) {
         obj = elem.getAsJsonObject();
       }
       catch (JsonSyntaxException e) {
-        FlutterUtils.warn(LOG, "Unable to parse JSON from Flutter test", e);
+        FlutterUtils.warn(LOG, "Unable to parse JSON from Flutter test", e, true);
         return;
       }
 
@@ -342,5 +343,5 @@ private void dispatchJson(String json) {
     }
   }
 
-  private static final @NotNull Logger LOG = Logger.getInstance(FlutterTestRunner.class);
+  private static final @NotNull Logger LOG = PluginLogger.createLogger(FlutterTestRunner.class);
 }