SystemServer+LoginServer+Userland: Switch to sid-based sockets

This commit does three things atomically:
- switch over Core::Account+SystemServer+LoginServer to sid based socket
  names.
- change socket names with %uid to %sid.
- add/update necessary pledges and unveils.

Userland: Switch over servers to sid based sockets

Userland: Properly pledge and unveil for sid based sockets

Userland/Applets/ClipboardHistory/main.cpp

@@ -17,7 +17,7 @@
 
 ErrorOr<int> serenity_main(Main::Arguments arguments)
 {
-    TRY(Core::System::pledge("stdio recvfd sendfd rpath unix"));
+    TRY(Core::System::pledge("stdio recvfd sendfd rpath unix proc"));
     auto app = TRY(GUI::Application::try_create(arguments));
 
     Config::pledge_domain("ClipboardHistory");