Reduce AlltoAll port usage in send/recv proxy (#577)

* Reduce AlltoAll port usage when connecting proxy

Reuse socket ports when connecting proxies in AlltoAll.

Existing port usage in AlltoAll is O(n) for recv and O(n) for send,
reusing socket ports in server or client side will make one of them
O(1), reusing both will reduce the total port usage to O(1) and enables
AlltoAll in >64 MI200 nodes.

* Update changelog accordingly

Update changelog accordingly.

src/include/socket.h

@@ -51,7 +51,7 @@ int ncclFindInterfaces(char* ifNames, union ncclSocketAddress *ifAddrs, int ifNa
 // Create a listening socket. sock->addr can be pre-filled with IP & port info. sock->fd is set after a successful call
 ncclResult_t ncclSocketListen(struct ncclSocket* sock);
 // Connect to sock->addr. sock->fd is set after a successful call.
-ncclResult_t ncclSocketConnect(struct ncclSocket* sock);
+ncclResult_t ncclSocketConnect(struct ncclSocket* sock, int portReuse = 0);
 // Return socket connection state.
 ncclResult_t ncclGetSocketState(struct ncclSocket* sock, enum ncclSocketState* state);
 // Accept an incoming connection from listenSocket->fd and keep the file descriptor in sock->fd, with the remote side IP/port in sock->addr.