Align template API with dictionary API (#13714)

* Align the template services and API with the dictionary ones (use attempt pattern)

* A little controller clean-up

* Mimic old file service behavior, make unit tests happy

* Align CreateForContentTypeAsync return value with the rest of the TemplateService API

* Scaffold endpoint should no longer feature master templates

* Update the OpenAPI JSON

tests/Umbraco.Tests.Integration/Testing/UmbracoIntegrationTest.cs

@@ -197,4 +197,14 @@ public abstract class UmbracoIntegrationTest : UmbracoIntegrationTestBase
             configBuilder.AddConfiguration(GlobalSetupTeardown.TestConfiguration);
         }
     }
+
+    protected void DeleteAllTemplateViewFiles()
+    {
+        var fileSystems = GetRequiredService<FileSystems>();
+        var viewFileSystem = fileSystems.MvcViewsFileSystem!;
+        foreach (var file in viewFileSystem.GetFiles(string.Empty).ToArray())
+        {
+            viewFileSystem.DeleteFile(file);
+        }
+    }
 }