Implement SrvGetThreadConsoleDesktop

A quick glance at https://reactos.org/testman/detail.php?id=33092394 and later at
https://git.reactos.org/?p=reactos.git;a=blob;f=reactos/win32ss/user/winsrv/usersrv/init.c;hb=569bc9fb4779c6291cb35039f3eba4561d6be662#l121
and
https://svn.reactos.org/svn/reactos/trunk/reactos/include/reactos/subsys/win/winmsg.h?view=diff&r1=65512&r2=65513&pathrev=65513

leads me to believe that SrvGetThreadConsoleDesktop can be implemented as follows

 GetThreadConsoleDesktopRequest->ConsoleDesktop = GetThreadDesktop(GetThreadConsoleDesktopRequest->ThreadId);

GetThreadDesktop, GetConsoleWindow from kernel32
probably fixing a few tests.