CLI reports "Cordova Platforms : none" although platforms are installed

I noticed more and more posts in the forum that do include `ionic info` output to report "Cordova Platforms : none":
https://forum.ionicframework.com/search?q=%22cordova%20platforms%22%20none%20order%3Alatest

See these two posts for a good example:
https://forum.ionicframework.com/t/windows-10-sdk-missing/126215/3
https://forum.ionicframework.com/t/windows-10-sdk-missing/126215/5

So while `ionic info` is reporting that no platforms are installed, in reality there are platforms already added to the project which can be seen from the `ionic cordova platform list` output.

先在已加入平台的專案中執行 `ionic info` 和 `ionic cordova platform list`，然後追蹤產生各項輸出的 CLI 入口點。比較每個命令偵測已安裝平台的方式，並讓 `ionic info` 回報相同的平台；根據所回報的 Windows SDK 情境驗證結果。

由索引模型根據 Issue 內容生成。