Add virtual chat API methods in Shared (#40895)

* move chat stuff to shared

* refactor: using cleanup +whitespaces + xml-doc

* review

---------

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

Content.Server/NPC/HTN/PrimitiveTasks/Operators/SayKeyOperator.cs

@@ -1,4 +1,5 @@
 using Content.Server.Chat.Systems;
+using Content.Shared.Chat;
 
 namespace Content.Server.NPC.HTN.PrimitiveTasks.Operators;