Test: filter to the extension viewlet for extensions that do not support a virtual file system

[aeschli]

Ref #123905

• anyOS @gregvanl
• anyOS @joaomoreno

Complexity: 3

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• install the RemoteHub extension
• open a GitHub Repository
• verify that the remote indicator says GiitHub.
• verify that the hover on the remote indicator is a custom hover and contains a link that opens the extensions view
• very that the extensions view opens with the @workspaceUnsupported grouping and show extensions that are disabled in virtual workspaces and extensions that are limited in virtual workspaces