Migrate VSCode Configuration Editor using the new WebView UI Toolkit

VSCode introduced a new WebView UI Toolkit that we can use to replace our current Configuration Editor.

Our current implementation requires us to maintain our own styles and is essentially copying VSCode look and feel; however, this will be challenging to maintain in the long run, and is something we can now avoid with the new UI toolkit.

Using this toolkit will ensure out plugin is adhering to VSCode UI standards and practices, and we will not need to maintain our own look & feel.

We first need to ensure the toolkit has everything we need.

https://code.visualstudio.com/blogs/2021/10/11/webview-ui-toolkit