[Core] Add counter information for project build errors

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/978115

Author: Therzok

main/src/core/MonoDevelop.Core/MonoDevelop.Projects/Project.cs

@@ -1607,11 +1607,17 @@ void AddRunMSBuildTargetTimerMetadata (
 
 			metadata.FirstBuild = IsFirstBuild;
 
-			bool success = false;
+			bool success = true;
 			bool cancelled = false;
 
 			if (result != null) {
-				success = !result.Errors.Any (error => !error.IsWarning);
+				foreach (var error in result.Errors) {
+					bool isError = !error.IsWarning;
+					if (isError) {
+						success = false;
+						metadata.RegisterError (error.Code);
+					}
+				}
 
 				if (!success) {
 					cancelled = result.Errors [0].Message == "Build cancelled";

main/src/core/MonoDevelop.Core/MonoDevelop.Projects/SolutionItem.cs

@@ -1890,5 +1890,18 @@ public bool Cancelled {
 			get => GetProperty<bool> ();
 			set => SetProperty (value);
 		}
+
+		Dictionary<string, int> errors;
+
+		public void RegisterError(string errorCode)
+		{
+			if (errors == null) {
+				errors = new Dictionary<string, int> ();
+				SetProperty (errors, "Errors");
+			}
+
+			errors.TryGetValue (errorCode, out int value);
+			errors [errorCode] = value + 1;
+		}
 	}
 }