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. :^)
Instead of passing the BufferStream, pass the Decoder. I'd like to stop
using BufferStream eventually anyway, so it's good to get it out of any
API's where it's in currently.
This shaves ~5 seconds off of a full build, not too bad. Also it just
seems nicer to push this logic out to classes. It could be better but
it's a start. :^)
