V11: Fix decimal variants (#13741)

* fix sqlite with variants

* Create and register SqlSpecificMapper

* Delete obsolete file

* Add back inheritance

Co-authored-by: Zeegaan <nge@umbraco.dk>
(cherry picked from commit c868c60ed2)

src/Umbraco.Infrastructure/Mapping/UmbracoDefaultMapper.cs

@@ -0,0 +1,30 @@
+using System.Globalization;
+using NPoco;
+
+namespace Umbraco.Cms.Core.Mapping;
+
+public class UmbracoDefaultMapper : DefaultMapper
+{
+    public override Func<object, object?> GetFromDbConverter(Type destType, Type sourceType)
+    {
+        if (destType == typeof(decimal))
+        {
+            return value =>
+            {
+                var result = Convert.ToDecimal(value, CultureInfo.InvariantCulture);
+                return result;
+            };
+        }
+
+        if (destType == typeof(decimal?))
+        {
+            return value =>
+            {
+                var result = Convert.ToDecimal(value, CultureInfo.InvariantCulture);
+                return result;
+            };
+        }
+
+        return base.GetFromDbConverter(destType, sourceType);
+    }
+}