fix, windows try kill flutter main window process only when --server's ipc is occupied

[21pages]

#8077

It can't be reproduced, so I make special exes to simulate it.

Test step:

1. Make a special exe that --server will delay start ipc so that main window process have enough time to occupy the ipc, and install the exe.
2. If main window occupy the ipc, it'll receive the close message from --service and call std::process::exit, If I change the multi window plugin and make it always prevent close, std::process::exit still work, in order to reproduce the occupying, make a special exe that remove the line std::process::exit, so that the main window can't be killed by --service. So this pr fix the condition that std::process::exit not work.
   

   rustdesk/src/ipc.rs

   Line 362 in c2b7810

   std::process::exit(0);

3. Kill the --server process and start the special main window process right now.
4. If the installed exe is based on master, --server will be restarted in a loop; If the installed exe is based on pr, --server will kill the main window process when it finds that its ipc is occupied.

based_on_master.mp4

based_on_pr.mp4