This actually addresses the real issue that was ignored earlier about
pipes on Windows. The FileHandle cannot provide a non-owning file
descriptor (the returned file descriptor would need to be explicitly
`_close`'d by the receiver). Foundation now vends a `_handle` accessor
to the OS primitive handle. Use this to create the dispatch loop for
messaging. We now create the JSONRPCConnection from handles on Windows
which actually should help enable running some of the tests on Windows
as well.
We will be able to split the LSP modules off later. These LSP modules
will provide the ability to write custom LSP servers and clients in
Swift. The sourcekit-lsp repository will build on top of this new
package to provide an LSP implementation that creates a language server
for Swift and C-based-languages.
