Properly implement Debug for Window and EventLoop types (#3297)

For EventLoop, EventLoopBuilder, EventLoopProxy and by requiring it as
a supertrait of Window and ActiveEventLoop.

It is especially useful for user to be able to know that Window is Debug.

src/platform_impl/linux/wayland/event_loop/mod.rs

@@ -45,6 +45,7 @@ pub(crate) enum Event {
 }
 
 /// The Wayland event loop.
+#[derive(Debug)]
 pub struct EventLoop {
     /// Has `run` or `run_on_demand` been called or a call to `pump_events` that starts the loop
     loop_running: bool,
@@ -546,6 +547,7 @@ impl AsRawFd for EventLoop {
     }
 }
 
+#[derive(Debug)]
 pub struct ActiveEventLoop {
     /// Event loop proxy
     event_loop_proxy: CoreEventLoopProxy,
@@ -665,6 +667,7 @@ impl rwh_06::HasDisplayHandle for ActiveEventLoop {
     }
 }
 
+#[derive(Debug)]
 pub struct OwnedDisplayHandle {
     pub(crate) connection: Connection,
 }

src/platform_impl/linux/wayland/event_loop/proxy.rs

@@ -7,6 +7,7 @@ use sctk::reexports::calloop::ping::Ping;
 use crate::event_loop::{EventLoopProxy as CoreEventLoopProxy, EventLoopProxyProvider};
 
 /// A handle that can be sent across the threads and used to wake up the `EventLoop`.
+#[derive(Debug)]
 pub struct EventLoopProxy {
     ping: Ping,
 }

src/platform_impl/linux/wayland/event_loop/sink.rs

@@ -8,7 +8,7 @@ use crate::window::WindowId;
 
 /// An event loop's sink to deliver events from the Wayland event callbacks
 /// to the winit's user.
-#[derive(Default)]
+#[derive(Default, Debug)]
 pub struct EventSink {
     pub(crate) window_events: Vec<Event>,
 }