Add virtual chat API methods in Shared (#40895)

* move chat stuff to shared

* refactor: using cleanup +whitespaces + xml-doc

* review

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Co-authored-by: pa.pecherskij <pa.pecherskij@interfax.ru>

Content.Server/Administration/Commands/OSay.cs

@@ -2,6 +2,7 @@ using System.Linq;
 using Content.Server.Administration.Logs;
 using Content.Server.Chat.Systems;
 using Content.Shared.Administration;
+using Content.Shared.Chat;
 using Content.Shared.Database;
 using Robust.Shared.Console;