Fix misleading `getDesiredResourceTags` behavior

https://github.com/aws-cloudformation/cloudformation-cli-java-plugin/blob/75133adfd5b82c347bf31579b09e82750b47cde7/src/main/java/software/amazon/cloudformation/AbstractWrapper.java#L536-L549

Here we claim `getDesiredResourceTags` return User-defined tags. Intuitively readers would assume it's for user tags only.

However, I have noticed system tags such as `aws:cloudformation:stackid` is being added in the returned results while testing my CFN stack. Given we already have `request.getRequestData().getSystemTags()` method for system tags, please consider to either update the code comments explaining why these non User-defined tags are here, or provide another method that will only return user tags to avoid confusions.