cleanup: remove the 'numsocks' argument used in many places

It was used (intended) to pass in the size of the 'socks' array that is
also passed to these functions, but was rarely actually checked/used and
the array is defined to a fixed size of MAX_SOCKSPEREASYHANDLE entries
that should be used instead.

Closes #4169

lib/asyn-thread.c

@@ -626,8 +626,7 @@ CURLcode Curl_resolver_is_resolved(struct connectdata *conn,
 }
 
 int Curl_resolver_getsock(struct connectdata *conn,
-                          curl_socket_t *socks,
-                          int numsocks)
+                          curl_socket_t *socks)
 {
   int ret_val = 0;
   time_t milli;
@@ -639,7 +638,6 @@ int Curl_resolver_getsock(struct connectdata *conn,
 #else
   (void)socks;
 #endif
-  (void)numsocks;
 
 #ifdef HAVE_SOCKETPAIR
   if(td) {