zbus-2.0.0-beta.3

• More reliable implementation of azync::Connection::receive_specific, which is heavily relied on by other async API. There was certain situations in which caller will end up waiting forever for a message that was already received (IOW an async deadlock).
• Ability to register multiple handlers for the same signal on the same proxy. This also implies dropping of disconnect_signal wrappers from macro generated proxy code since now each registered handler has a unique ID, with which can disconnect the handler. This is an API break as all of the signal handler disconnection code will need to be changed.
• Take signal sender into account. While in most cases this isn't necessary, it becomes very important when communicating with multiple services exposing the same interface, over the same connection.
• std::convert::Infallible to Error. Strictly speaking, this is an API break since error type inference in certain cases won't work and user will have to explicitly specify error types.
• Allow passing ObjectPath itself to parameters expecting TryInto<ObjectPath>. This fixes a regression from the previous pre-release where we made it easier to use the API by simply passing a string (the typical case).
• Expose zbus::fdo::Properties interface implementation.
• Internal signal subscription mechanism that ensures proxies to the same destination don't end up unsubscribing each other.
• Wrap serde_xml_rs::Error in zbus::Error. This is an API break, but with moderate impact, since callers usually can't do much with the XML error.
• SignalReceiver::receive_for now returns a Result<()>. This is strictly speaking an API break as existing code will get a warning from the compiler about unused Result from this call.
• Re-export serde.
• Add Debug impl on azync::SignalStream.
• Add dependency on:
  • slotmap
  • event-listener
• Other minor internals fixes/improvements.