Work around account switching failing to open the CEF debugger socket (#668)

* Work around account switching failing to open the CEF debugger socket

this automates lsof and gdb to force close the socket before steam finishes shutting down (from RegisterForShutdownStart)

* lint

* fix LD_LIBRARY_PATH for gdb

backend/decky_loader/localplatform/localplatformwin.py

@@ -55,4 +55,7 @@ def get_unprivileged_user() -> str:
     return os.getenv("UNPRIVILEGED_USER", os.getlogin())
 
 async def restart_webhelper() -> bool:
-    return True # Stubbed
+    return True # Stubbed
+
+async def close_cef_socket():
+    return # Stubbed