GH-3530: The Oracle driver does not implement DbDataReader.Get* metho…

…ds. Encapsulate their DbDataReader with the DirectCastDbDataReader.

src/NHibernate/Driver/OracleDataClientDriverBase.cs

@@ -35,7 +35,7 @@ protected override DbDataReader ExecuteDbDataReader(CommandBehavior behavior)
 				var reader = Command.ExecuteReader(behavior);
 				_suppressDecimalInvalidCastExceptionSetter(reader, true);
 
-				return reader;
+				return new DirectCastDbDataReader(reader);
 			}
 		}