embassy_sync/pubsub: fix PubSubBehavior visibility

https://github.com/embassy-rs/embassy/pull/2969 appears to have broken
direct `publish_immediate()` on `pubsub::Channel`, as it functionally
made `PubSubBehavior` private and didn't delegate this method to the new
(private) `SealedPubSubBehavior`.

This change moves `publish_immediate`, `capacity`, and `is_full` from
`SealedPubSubBehavior` to `PubSubBehavior` in order to restore them to
`pub` visibility.

embassy-sync/src/pubsub/mod.rs

@@ -194,6 +194,25 @@ impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usi
     }
 }
 
+impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usize> crate::pubsub::PubSubBehavior<T>
+    for PubSubChannel<M, T, CAP, SUBS, PUBS>
+{
+    fn publish_immediate(&self, message: T) {
+        self.inner.lock(|s| {
+            let mut s = s.borrow_mut();
+            s.publish_immediate(message)
+        })
+    }
+
+    fn capacity(&self) -> usize {
+        self.capacity()
+    }
+
+    fn is_full(&self) -> bool {
+        self.is_full()
+    }
+}
+
 impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usize> SealedPubSubBehavior<T>
     for PubSubChannel<M, T, CAP, SUBS, PUBS>
 {
@@ -246,13 +265,6 @@ impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usi
         })
     }
 
-    fn publish_immediate(&self, message: T) {
-        self.inner.lock(|s| {
-            let mut s = s.borrow_mut();
-            s.publish_immediate(message)
-        })
-    }
-
     fn unregister_subscriber(&self, subscriber_next_message_id: u64) {
         self.inner.lock(|s| {
             let mut s = s.borrow_mut();
@@ -267,10 +279,6 @@ impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usi
         })
     }
 
-    fn capacity(&self) -> usize {
-        self.capacity()
-    }
-
     fn free_capacity(&self) -> usize {
         self.free_capacity()
     }
@@ -286,10 +294,6 @@ impl<M: RawMutex, T: Clone, const CAP: usize, const SUBS: usize, const PUBS: usi
     fn is_empty(&self) -> bool {
         self.is_empty()
     }
-
-    fn is_full(&self) -> bool {
-        self.is_full()
-    }
 }
 
 /// Internal state for the PubSub channel
@@ -445,8 +449,6 @@ pub enum Error {
     MaximumPublishersReached,
 }
 
-/// 'Middle level' behaviour of the pubsub channel.
-/// This trait is used so that Sub and Pub can be generic over the channel.
 trait SealedPubSubBehavior<T> {
     /// Try to get a message from the queue with the given message id.
     ///
@@ -462,12 +464,6 @@ trait SealedPubSubBehavior<T> {
     /// If the queue is full and a context is given, then its waker is registered in the publisher wakers.
     fn publish_with_context(&self, message: T, cx: Option<&mut Context<'_>>) -> Result<(), T>;
 
-    /// Publish a message immediately
-    fn publish_immediate(&self, message: T);
-
-    /// Returns the maximum number of elements the channel can hold.
-    fn capacity(&self) -> usize;
-
     /// Returns the free capacity of the channel.
     ///
     /// This is equivalent to `capacity() - len()`
@@ -482,9 +478,6 @@ trait SealedPubSubBehavior<T> {
     /// Returns whether the channel is empty.
     fn is_empty(&self) -> bool;
 
-    /// Returns whether the channel is full.
-    fn is_full(&self) -> bool;
-
     /// Let the channel know that a subscriber has dropped
     fn unregister_subscriber(&self, subscriber_next_message_id: u64);
 
@@ -495,9 +488,16 @@ trait SealedPubSubBehavior<T> {
 /// 'Middle level' behaviour of the pubsub channel.
 /// This trait is used so that Sub and Pub can be generic over the channel.
 #[allow(private_bounds)]
-pub trait PubSubBehavior<T>: SealedPubSubBehavior<T> {}
+pub trait PubSubBehavior<T>: SealedPubSubBehavior<T> {
+    /// Publish a message immediately
+    fn publish_immediate(&self, message: T);
 
-impl<T, C: SealedPubSubBehavior<T>> PubSubBehavior<T> for C {}
+    /// Returns the maximum number of elements the channel can hold.
+    fn capacity(&self) -> usize;
+
+    /// Returns whether the channel is full.
+    fn is_full(&self) -> bool;
+}
 
 /// The result of the subscriber wait procedure
 #[derive(Debug, Clone, PartialEq, Eq)]