Better support for moving Calva Inspector around

[skylize]

Calva Inspector's current implementation as a TreeView gives it limited and clunky ability to get moved around the screen. Would be nice if it had more freedom.

[PEZ]

This is fundamentally a VS Code issue. All views have limitations on where they can be placed. I think only the terminals have almost full freedom. The API does not let an extension change this.

The way some extensions (the VS Code internal CoPilot extension included) solve it by a separate command for opening a view in the editor area. Because Sidebar and panel views can be dragged between sidebar and panel, but not to the editor area. And editors can't be dragged to the sidebar. (It is beyond me why anyone thinks these limitations are a good idea, but that's a subject for a separate discussion.)

In order to create a view that can be hosted in the editor area, we need to create it using a vscode WebView. This is a pretty huge undertaking, but has several other benefits (such as full freedom to design the Ux in the view).