sceNetInet: errno per thread as on hardware, and the socket table

errno:
- A thread that hasn't made a call yet reads 0x80410001 from GetErrno,
  as the PSP has no errno record for it until then. errno is saved in
  savestates now, in a new sceNet section version.
- socket(), close() and setsockopt() clear it when they succeed.
- Running out of descriptors is EMFILE, at 255 like the PSP, and an
  unconnected UDP socket sending without an address EDESTADDRREQ, which
  Winsock calls ENOTCONN.
- On Windows, ENOBUFS, EPROTOTYPE, ENOPROTOOPT, EMSGSIZE, ENETRESET and
  EDESTADDRREQ now map to the PSP's errnos. They only did elsewhere.
All from pspautotests net/inet/errors, options and errnothread.

The socket table:
- Descriptor numbers are handed out round-robin up to 255, as on the PSP
  (net/inet/states), rather than the lowest free one.
- Closing frees the slot even if the host's close fails, and Close and
  CloseAll take the lock the rest of SocketManager does.
- accept no longer leaks the host socket when it runs out of numbers.
- bind no longer asks UPnP to forward port 0, and closing the socket
  removes its forward, unless another socket still uses the port.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Core/HLE/sceNet.cpp

@@ -713,7 +713,7 @@ void netValidateLoopMemory() {
 
 // This feels like a dubious proposition, mostly...
 void __NetDoState(PointerWrap &p) {
-	auto s = p.Section("sceNet", 1, 8);
+	auto s = p.Section("sceNet", 1, 9);
 	if (!s)
 		return;
 
@@ -781,7 +781,7 @@ void __NetDoState(PointerWrap &p) {
 		apctlEvents.clear();
 		apctlProdCodeAddr = 0;
 	}
-	__NetInetDoState(p, s >= 8);
+	__NetInetDoState(p, s >= 8, s >= 9);
 
 	if (p.mode == p.MODE_READ) {
 		// Let's not change "Inited" value when Loading SaveState in the middle of multiplayer to prevent memory & port leaks