support execute_batch (#216)

Rails is using `execute_batch` when truncating tables and loading fixtures.

https://github.com/rails/rails/blob/bab99f8b51dfbff4d9e161b8f23c0dbf5d3b9314/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb#L232

https://github.com/rails/rails/blob/bab99f8b51dfbff4d9e161b8f23c0dbf5d3b9314/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb#L515

But since this gem is changing signature of `raw_execute`, then it does not work out of the box and needs to call `execute` instead.

https://github.com/rails/rails/blob/bab99f8b51dfbff4d9e161b8f23c0dbf5d3b9314/activerecord/lib/active_record/connection_adapters/abstract/database_statements.rb#L616-L620

Author: mikz

lib/active_record/connection_adapters/clickhouse/schema_statements.rb

@@ -47,6 +47,12 @@ def execute(sql, name = nil, format: @response_format, settings: {})
           end
         end
 
+        def execute_batch(statements, name = nil, **kwargs)
+          statements.each do |statement|
+            execute(statement, name, **kwargs)
+          end
+        end
+
         def exec_insert(sql, name = nil, _binds = [], _pk = nil, _sequence_name = nil, returning: nil)
           new_sql = sql.sub(/ (DEFAULT )?VALUES/, " VALUES")
           with_response_format(nil) { execute(new_sql, name) }