V15: Dont create invalid media (#17534)

* Don't allow create when there is validation errors

* Fix tests

* Add tests

* Fix last test

* Fix more tests

---------

Co-authored-by: Jacob Overgaard <752371+iOvergaard@users.noreply.github.com>

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

@@ -70,6 +70,8 @@ public abstract class UmbracoIntegrationTestWithMediaEditing : UmbracoIntegratio
         var mediaTypes = MediaTypeService.GetAll();
         var mediaTypesList = mediaTypes.ToList();
         var imageMediaType = mediaTypesList.FirstOrDefault(x => x.Alias == "Image");
+        imageMediaType.PropertyTypes.First().Mandatory = false;
+        MediaTypeService.Save(imageMediaType);
 
         // Add CustomMediaType to FolderMediaType AllowedContentTypes
         var mediaTypeUpdateHelper = new MediaTypeUpdateHelper();