io: use io_uring for all io

There should no longer be any

- read
- write
- connect
- sendmsg
- recvmsg
- accept

calls in the codebase. Previously we were using a mix of io_uring and
these calls which had some negative effects: Since we were using the old
system calls, we had to set the file descriptors to non-blocking. But
our io_uring code did not handle EAGAIN. This lead to programs sometimes
being killed when the wayland IO was actually blocking.

Now all file descriptors are set to blocking, but io_uring makes it
non-blocking from our perspective. The one exception are evdev files
because they are read via libinput and libinput uses the old system
calls.

src/dbus/socket.rs

@@ -404,7 +404,13 @@ impl DbusSocket {
         msg.marshal(&mut fmt);
         let body_len = (buf.len() - body_start) as u32;
         buf[4..8].copy_from_slice(uapi::as_bytes(&body_len));
-        (BufIoMessage { fds, buf }, serial)
+        (
+            BufIoMessage {
+                fds,
+                buf: buf.unwrap(),
+            },
+            serial,
+        )
     }
 
     fn format_header(
@@ -489,7 +495,7 @@ where
     ) -> Result<(), DbusError> {
         let msg = <T::Generic<'a> as Message>::unmarshal(parser)?;
         (self.0)(Ok(&msg));
-        socket.bufio.add_buf(buf);
+        socket.in_bufs.push(buf);
         Ok(())
     }
 }