This is to allow future changes to do cross-process MessagePorts in an
implementation-agnostic way. Add some tests for this behavior.
Delivering messages that were posted to a MessagePort just before it was
transferred is not yet implemented still.
Use a LocalSocket to represent the connection between two message ports.
The concept of the port message queue is still missing, however. When
that concept is implemented, the "steps" in step 7 of the message port
transfer steps will need to send the serialized data over the connected
socketpair and run in the event loop of the process that holds onto the
other side of the message port. Doing this should allow centralizing the
behavior of postMessage for Window, MessagePorts and Workers.
The intent is to use these to autogenerate prototype declarations for
Window and WorkerGlobalScope classes.
And the spec links are just nice to have :^)
This patch adds a basic initial implementation of these API's.
Since LibWeb currently doesn't support workers, this implementation of
messaging doesn't bother with serializing and deserializing messages.
