Check for plugin activation when uninstalling plugins

[colin-grant-work]

Following #11084, it would be desirable to ensure that plugins that have not been activated are simply uninstalled and do not show a 'Reload Required' notice on the frontend.

Original comment:

Aside from that I noticed that every uninstalled extension now requires to reload before disappearing completely. While this is definitely an improvement to the way it worked previously, vscode seems to be able to decide on a case-by-case basis whether uninstalling an extension requires an app reload. But this is probably something for another PR :)

Originally posted by @msujew in #11084 (review)