Tests whether a symbol is registered as an exception type
ExceptionTypeRegisteredQ[sym]
ExceptionTypeRegisteredQ[sym, tag]
ExceptionTypeRegisteredQ[sym, {tag1, tag2, …}]
ExceptionTypeRegisteredQ /@ {TypeConversionError, tag}
→ {False, False}ExceptionTypeRegisteredQ /@ {DatabaseError, DatabaseTypeError, "GeneralError"}
→ {False, False, False}