This fixes an issue where webviews for custom editors did not have any associated extension information, which caused them try reading `file:` uri resources instead of remote uri resources
- make it unlikely that a new view instance would accept a view zone id from a previous view instance
- remove that the find widget removes a view zone id from another view
(fixes#71745)
This change attempts to do the following:
- Encapsult most of the logic for handling the webviews used for webview editors into a new WebviewEditorOverlay class
- Greatly simplify WebviewEditorInput and make it take a webview when it is created
- Move the webview creation logic up into the webviewEditorService instead of having it be inside the webviewEditor class itself
This aim of these changes is to make it possible to re-use more of the webview logic for custom editors
