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.

閱讀 src/main/java/software/amazon/cloudformation/AbstractWrapper.java 的第536-549行，然後檢查 request.getRequestData().getSystemTags()，以比較標籤來源。確認現有行為應予以文件化，還是應在僅處理使用者標籤的方法後方加以分離；完成標準是 API 對系統標籤的處理方式明確無歧義。

由索引模型根據 Issue 內容生成。