runtime: command: add an arg to begin_processing() to indicate pipeline position

bshell.runtime/command/function.c

@@ -43,7 +43,9 @@ static enum bshell_status get_callable_name(
 	return BSHELL_SUCCESS;
 }
 
-static enum bshell_status begin_processing(bshell_command *cmd)
+static enum bshell_status begin_processing(
+	bshell_command *cmd,
+	enum bshell_command_position position)
 {
 	return BSHELL_SUCCESS;
 }