Kernel: Cleanup and optimize TCP

We now only send enough data to fill other ends window, not past that.
Previous logic had a but that allowed sending too much data leading to
retransmissions.

When the target sends zero window and later updates window size,
immediately retransmit non-acknowledged bytes.

Don't validate packets through listeing socket twice. The actual socket
will already verify the checksum so the listening socket does not have
to.

kernel/include/kernel/Networking/TCPSocket.h

@@ -117,6 +117,7 @@ namespace Kernel
 			uint64_t					last_send_ms	{ 0 }; // last send time, used for retransmission timeout
 
 			bool						has_ghost_byte { false };
+			bool						had_zero_window { false };
 
 			uint32_t					data_tail 		{ 0 };
 			uint32_t					data_size		{ 0 }; // number of bytes in this buffer
@@ -179,6 +180,8 @@ namespace Kernel
 		bool m_keep_alive { false };
 		bool m_no_delay { false };
 
+		bool m_should_send_ack { false };
+
 		uint64_t m_time_wait_start_ms { 0 };
 
 		ThreadBlocker m_thread_blocker;