[testing] Enhancement: Improve tcp-echo

[iyzhang]

Remove data structure from tcp-echo that impacts performance.

[github-actions]

libos = catnap
commit id = 9194a6a

collapsed_stack	num_calls	cycles_per_call	nanoseconds_per_call	percent_time
bgc::catnap::transport::epoll	13360296.10	2006.72	889.33	32.06
register	14016.25	41.61	18.30	0.00
unregister	14015.25	50.33	22.14	0.00
demikernel::sgafree	11536.09	73.15	31.65	0.04
demikernel::sgaalloc	11283.68	115.73	51.31	0.09
ioc::network::libos::push;catnap::linux::transport::push	9066.12	664.71	294.81	4.16
ioc::network::libos::push	8800.49	16633.40	7385.04	5.45
demikernel::push	8800.49	561.63	247.89	0.14
ioc::network::libos::pop;catnap::linux::transport::pop	8024.13	421.55	184.09	4.23
ioc::network::libos::pop	7815.65	17722653.37	7906350.23	25.67
demikernel::pop	7815.65	550.57	238.59	0.10
ioc::network::libos::pushto	607.67	7354.68	3082.27	23.54
ioc::network::libos::pushto;catnap::linux::transport::push	607.67	454.61	190.39	6.18
demikernel::pushto	607.67	441.10	184.91	1.42
demikernel::async_close	32.50	1140.58	468.11	0.01
ioc::network::libos::connect	24.95	6927586.56	3083425.16	27.98
ioc::network::libos::connect;catnap::linux::transport::connect	24.95	75968.89	33572.92	2.57
demikernel::connect	24.95	1976.44	880.30	0.01
ioc::network::libos::close	18.35	24736.55	10815.14	0.07
ioc::network::libos::close;catnap::linux::transport::close	18.35	23362.12	10212.29	94.54
demikernel::accept	15.42	1447.89	631.41	0.00
ioc::network::libos::accept	15.39	909191451.93	395944537.39	46.18
ioc::network::libos::accept;catnap::linux::transport::accept	15.39	5088.10	2280.52	0.00
demikernel::socket	9.50	153126.52	67804.40	0.31
demikernel::socket;catnap::linux::transport::socket	9.50	150675.85	66733.15	96.39
demikernel::new	1.00	262683.56	114636.24	0.14
demikernel::bind	1.00	28978.02	12580.07	0.01
demikernel::bind;catnap::linux::transport::bind	1.00	24362.58	10575.86	84.04
demikernel::listen	1.00	14968.29	6496.53	0.00
demikernel::listen;catnap::linux::transport::listen	1.00	14041.08	6095.77	93.78
demikernel::close	0.00	nan	nan	0.00