This abstraction will help us to support multiple IPC transport
mechanisms going forward. For now, we only have a TransportSocket that
implements the same behavior we previously had, using Unix Sockets for
IPC.
Ladybird's HelperProcess.cpp was the only user of the IPCProcess class.
Moving the helper class from LibCore allows for some more interesting
LibIPC changes in the upcoming commits.
This large commit also refactors LibWebView's process handling to use
a top-level Application class that uses a new WebView::Process class to
encapsulate the IPC-centric nature of each helper process.
