feat: impl tcp unsend

fetch driver queue in binary

caller will recv
```
{Port, {data, ["?unsend?" | Binary]}}
````

Author: qzhuyan

erts/emulator/drivers/common/inet_drv.c

@@ -816,6 +816,7 @@ static size_t my_strnlen(const char *s, size_t maxlen)
 #define TCP_REQ_UNRECV         43
 #define TCP_REQ_SHUTDOWN       44
 #define TCP_REQ_SENDFILE       45
+#define TCP_REQ_UNSEND         46
 /* UDP and SCTP requests */
 #define PACKET_REQ_RECV        60 /* Common for UDP and SCTP         */
 /* #define SCTP_REQ_LISTEN       61 MERGED Different from TCP; not for UDP */
@@ -11904,6 +11905,25 @@ static ErlDrvSSizeT tcp_inet_ctl(ErlDrvData e, unsigned int cmd,
 	return ctl_reply(INET_REP_OK, NULL, 0, rbuf, rsize);
     }
 
+    case TCP_REQ_UNSEND: {
+    ErlIOVec iov;
+    ErlDrvSizeT sz;
+
+	DDBG(INETP(desc),
+	     ("INET-DRV-DBG[%d][" SOCKET_FSTR ",%T] tcp_inet_ctl -> UNSEND\r\n",
+	      __LINE__, desc->inet.s, driver_caller(desc->inet.port)) );
+	if (!IS_CONNECTED(INETP(desc)))
+   	    return ctl_error(ENOTCONN, rbuf, rsize);
+
+    sz = driver_peekqv(desc->inet.port, &iov);
+
+    if (sz > 0)
+    {
+        driver_outputv(desc->inet.port, "?unsend?", sizeof("?unsend?"), &iov, 0);
+    }
+
+	return ctl_reply(sz?INET_REP_OK:INET_REP_ERROR, NULL, 0, rbuf, rsize);
+    }
 
     case TCP_REQ_SHUTDOWN: {
 	int how;

erts/preloaded/ebin/prim_inet.beam

@@ -34,6 +34,7 @@
 -export([send/2, send/3, sendto/4, sendmsg/3, sendfile/4]).
 -export([recv/2, recv/3, async_recv/3]).
 -export([unrecv/2]).
+-export([unsend/2]).
 -export([recvfrom/2, recvfrom/3]).
 -export([setopt/3, setopts/2, getopt/2, getopts/2, is_sockopt_val/2]).
 -export([chgopt/3, chgopts/2]).
@@ -1468,6 +1469,18 @@ unrecv(S, Data) ->
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%
+%% UNSEND(insock(), data) -> ok | {error, Reason}
+%%
+%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+unsend(S, Data) ->
+    case ctl_cmd(S, ?TCP_REQ_UNSEND, Data) of
+	{ok, _} -> ok;
+	{error,_}=Error  -> Error
+    end.
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%
 %% DETACH(insock()) -> ok
 %%
 %%   unlink from a socket 

erts/preloaded/src/prim_inet.erl

@@ -102,6 +102,7 @@
 -define(TCP_REQ_UNRECV,         43).
 -define(TCP_REQ_SHUTDOWN,       44).
 -define(TCP_REQ_SENDFILE,       45).
+-define(TCP_REQ_UNSEND,         46).
 
 %% UDP and SCTP requests
 -define(PACKET_REQ_RECV,        60).