fix: Fix ApplyFiltering logic and add ResetToFirstPage

Author: DerekGooding

SimpleDataGrid/Pagination/PagedCollection.cs

@@ -388,6 +388,16 @@ private void ApplyFiltering(bool maintainPosition = false)
             _currentPage = 0;
         }
         RaiseAllChanged();
+
+        if (maintainPosition && _filtered.Any())
+        {
+            _currentPage = Math.Clamp(oldFirstItemIndex / _pageSize, 0, TotalPages - 1);
+        }
+        else
+        {
+            _currentPage = 0;
+        }
+        RaiseAllChanged();
     }
 
     private static string WildcardToRegex(string pattern)