[erts] Fix auto connect from net_kernel

This bug was harmless. Prior to ff7daac
(on master prior to OTP-26.0-rc3) net_kernel never triggered auto connect
itself. After that commit, when net_kernel triggered auto connect, the
runtime system would try-lock the main-lock on net_kernel while executing
net_kernel when sending a message to net_kernel. An assertion would trigger,
but in the optimized runtime this would just cause the try-lock to fail
and the message to unnecessarily to be placed in a heap-fragment.

erts/emulator/beam/dist.c

@@ -5589,6 +5589,9 @@ int erts_auto_connect(DistEntry* dep, Process *proc, ErtsProcLocks proc_locks)
             return 0;
         }
 
+        if (proc == net_kernel)
+            nk_locks |= ERTS_PROC_LOCK_MAIN;
+
         /*
          * Send {auto_connect, Node, DHandle} to net_kernel
          */
@@ -5599,6 +5602,10 @@ int erts_auto_connect(DistEntry* dep, Process *proc, ErtsProcLocks proc_locks)
         msg = TUPLE3(hp, am_auto_connect, dep->sysname, dhandle);
         ERL_MESSAGE_TOKEN(mp) = am_undefined;
         erts_queue_proc_message(proc, net_kernel, nk_locks, mp, msg);
+
+        if (proc == net_kernel)
+            nk_locks &= ~ERTS_PROC_LOCK_MAIN;
+
         erts_proc_unlock(net_kernel, nk_locks);
     }