Method on_callback_of_builtin

op_callback_of_builtin is an argument passed as a callback to an extern function `array_map('strlen')` where 'strlen' was wrapped into op_callback_of_builtin with str_val=strlen `array_map(fn(...)=>...)` where a lambda was wrapped into op_callback_of_builtin with bound_instance=lambda_class and str_val=__invoke `array_map($callback)` where a variable is wrapper into op_callback_of_builtin with bou