Bulk import switches for pk;import

We're now using binary import for switches and switch_members when importing a system profile, rather than importing them one switch at a time.

This adds a pass-through method to the PerformanceTrackingConnection that can be used for other bulk import applications.

PluralKit.Core/Utils.cs

@@ -488,6 +488,11 @@ namespace PluralKit
             _impl.Open();
         }
 
+        public NpgsqlBinaryImporter BeginBinaryImport(string copyFromCommand)
+        {
+            return _impl.BeginBinaryImport(copyFromCommand);
+        }
+
         public string ConnectionString
         {
             get => _impl.ConnectionString;