It is now possible to use the special IPC::File type in message arguments. In
C++, the type is nothing more than a wrapper over a file descriptor. But when
serializing/deserializing IPC::File arguments, LibIPC will use the sendfd/recvfd
kernel APIs instead of sending the integer inline.
This makes it quite convenient to pass files over IPC, and will allow us to
significantly tighten sandboxes in the future :^)
Closes https://github.com/SerenityOS/serenity/issues/3643
Now most classes dictate how they are serialized and deserialized when
transmitted across LibIPC sockets. This also makes the IPC compiler
a bit simpler. :^)
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. :^)
