This would previously fail at runtime, and it would have zero indication
of what exactly went wrong.
Also adds `AK::DependentFalse<Ts...>', which is a...dependent false.
Now most classes dictate how they are serialized and deserialized when
transmitted across LibIPC sockets. This also makes the IPC compiler
a bit simpler. :^)
Compiling anything that includes generated IPC messages is painfully
slow at the moment. This moves the encoding helpers out of line, which
helps a bit. Doing the same for decoding will help more.
