Deprecate `powershell.promptToUpdatePackageManagement` setting

[SeeminglyScience]

Also add deprecation messages to a few other settings. I'm guessing the ability to do so was not there when they were initially deprecated.

[SeeminglyScience]

@SydneyhSmith @andschwa just taggin' y'all so we remember we need to set me up to not trigger "needs triage"

[andyleejordan]

@SydneyhSmith @SeeminglyScience I think I set it up without any user exclusions, cause we still gotta triage our own issues. But if it's in a project or a milestone, then it won't get "Needs: Triage" (since that means it's been triaged).