Add POLLRDNORM/POLLWRNORM support.

On Linux these are meant to be equivalent to POLLIN/POLLOUT. Rather
than hack these on in sys_poll etc it felt cleaner to just cleanup
the call sites to notify for both events. This is what linux does
as well.

Fixes #5544

PiperOrigin-RevId: 364859977

pkg/sentry/fsimpl/fuse/connection.go

@@ -316,7 +316,7 @@ func (conn *connection) callFutureLocked(t *kernel.Task, r *Request) (*futureRes
 	conn.fd.completions[r.id] = fut
 
 	// Signal the readers that there is something to read.
-	conn.fd.waitQueue.Notify(waiter.EventIn)
+	conn.fd.waitQueue.Notify(waiter.ReadableEvents)
 
 	return fut, nil
 }

pkg/sentry/fsimpl/fuse/dev.go

@@ -368,10 +368,10 @@ func (fd *DeviceFD) readinessLocked(mask waiter.EventMask) waiter.EventMask {
 	}
 
 	// FD is always writable.
-	ready |= waiter.EventOut
+	ready |= waiter.WritableEvents
 	if !fd.queue.Empty() {
 		// Have reqs available, FD is readable.
-		ready |= waiter.EventIn
+		ready |= waiter.ReadableEvents
 	}
 
 	return ready & mask

pkg/sentry/fsimpl/fuse/dev_test.go

@@ -180,7 +180,7 @@ func ReadTest(serverTask *kernel.Task, fd *vfs.FileDescription, inIOseq usermem.
 
 	// Register for notifications.
 	w, ch := waiter.NewChannelEntry(nil)
-	dev.EventRegister(&w, waiter.EventIn)
+	dev.EventRegister(&w, waiter.ReadableEvents)
 	for {
 		// Issue the request and break out if it completes with anything other than
 		// "would block".

pkg/sentry/fsimpl/fuse/fusefs.go

@@ -286,7 +286,7 @@ func (fs *filesystem) Release(ctx context.Context) {
 	fs.umounted = true
 	fs.conn.Abort(ctx)
 	// Notify all the waiters on this fd.
-	fs.conn.fd.waitQueue.Notify(waiter.EventIn)
+	fs.conn.fd.waitQueue.Notify(waiter.ReadableEvents)
 
 	fs.conn.fd.mu.Unlock()