Add analyzer: Virtual member is never overridden

[xtqqczze]

Is there an issue tracking a Roslyn analyzer for: "virtual member is never overridden"?

https://www.jetbrains.com/help/resharper/VirtualMemberNeverOverridden.Global.html

Originally posted by @xtqqczze in #104483 (comment)

[buyaa-n]

New analyzer => moving to runtime.

@xtqqczze more details about how the analyzer should detect that Virtual member is never overridden would be appreciated

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[jeffhandley]

There's not enough information to make this actionable. For new analyzer suggestions, it's helpful to illustrate call sites where the diagnostic would show up as well as call sites where no diagnostic would appear.