Allow opting out of pre-release extensions in Insiders installs

[JacksonKearl]

Ref #138086
I use VS Code insiders because I trust the VS Code team to release generally-reasonable insiders builds and respond quickly to severe issues in them. Additionally, I expect that VS Code insiders will have bleeding-edge features that I want to use. None of these conditions are true for extensions. It'd be nice to have a way to say even though I'm on Insiders, I don't want my extension install button to default to Pre-Release.

[gjsjohnmurray]

Note 2 of the test issue mentions a setting to do this. But #138193 says it's not working, and in any case maybe you don't want it to be merely an 'internal' one.

[sandy081]

CC @isidorn

[isidorn]

Fair request. Nothing I think we should add before more users request it. I love the choice that the dropdown gives you, so the setting would just be convenience to not click on the dropdown...

[vscodenpa]

We closed this issue because we don't plan to address it in the foreseeable future. If you disagree and feel that this issue is crucial: we are happy to listen and to reconsider.

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Thanks for your understanding, and happy coding!