Improve performance of gvisor-tap-vsock port driver

[fahedouch]

Currently, using the gvisor-tap-vsock port driver adds a userspace TCP proxy, which reduces throughput from ~6.5 Gbit/s to ~4.0 Gbit/s due to extra copies and wakeups.

It seems possible to improve performance by using tunneling via `/services/tunnel in gvisor-tap-vsock. This approach would remove the TCP proxy and allow buffer control in rootlesskit, potentially reducing latency and increasing throughput.

Proposal:

• Investigate and implement port forwarding via tunnel in rootlesskit.
• Document possible performance impacts and any new bottlenecks.

[fahedouch]

the optimization is not straightforward. I propose implementing this for the next minor versions of v3. I want us to release it first and play with it in nerdctl.

@AkihiroSuda