C#: Make Started log as Debug.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp.Standalone/Extractor.cs

@@ -111,12 +111,12 @@ public void Analysed(int item, int total, string source, string output, TimeSpan
                     AnalysisAction.UpToDate => "up to date",
                     _ => "unknown action"
                 };
-                logger.LogInfo($"[{item}/{total}] {source} ({extra})");
+                logger.LogDebug($"[{item}/{total}] {source} ({extra})");
             }
 
             public void Started(int item, int total, string source)
             {
-                logger.LogInfo($"[{item}/{total}] {source} (processing started)");
+                logger.LogDebug($"[{item}/{total}] {source} (processing started)");
             }
 
             public void MissingType(string type)
@@ -166,4 +166,4 @@ public static ExitCode Run(Options options)
             return ExitCode.Ok;
         }
     }
-}
+}