Introduce socketpair abstraction for process local events

[elfenpiff]

Brief feature description

Since the WaitSet must support file descriptors, the event messaging pattern must be based on file descriptors. Currently, the process local variant uses non-process local unix datagram sockets which violate the process local contract.

This can be solved by creating an abstraction for socketpair() and implementing an event concept on them so that it can be used in process local services.

[elfenpiff]

See this for windows inspiration: https://github.com/sunfishcode/socketpair/blob/main/src/windows_async_std.rs