Update `add_timestamps_with_timezone`

In !73842 (comment 726372362), it was noted that add_timestamps_with_timezone may be in need of an update:

1. It only allows updated_at, created_at, deleted_at. Is there a reason to not use it to create columns like processed_at, read_at, etc...
2. It uses the deprecated add_column_with_default method.
3. I am suspicious we may not need to validate_not_in_transaction! anymore because of point (2.)