Automatically detect unused extensions

[dsseng]

Not a duplicate of #57548.
The idea is to detect extensions that weren't used for long time. E.g. if extension provides syntax support for language and it's not used in this workspace, VS Code should advise to disable it in workspace, globally or remove it. If extension adds commands and they weren't used for long, user should be notified too. This can help users reduce RAM/CPU usage and startup time.

[vscodebot]

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Happy Coding!