chore: expose hashed_bytes of KBucketKey

Pull-Request: #4698.

Author: maqi

protocols/kad/CHANGELOG.md

@@ -6,6 +6,8 @@
   See [PR 4503](https://github.com/libp2p/rust-libp2p/pull/4503).
 - Make previously "deprecated" `record` module private.
   See [PR 4035](https://github.com/libp2p/rust-libp2p/pull/4035).
+- Expose hashed bytes of KBucketKey.
+  See [PR 4698](https://github.com/libp2p/rust-libp2p/pull/4698).
 - Remove previously deprecated type-aliases.
   Users should follow the convention of importing the `libp2p::kad` module and referring to symbols as `kad::Behaviour` etc.
   See [PR 4733](https://github.com/libp2p/rust-libp2p/pull/4733). 

protocols/kad/src/kbucket/key.rs

@@ -77,6 +77,11 @@ impl<T> Key<T> {
         self.bytes.distance(other)
     }
 
+    /// Exposing the hashed bytes.
+    pub fn hashed_bytes(&self) -> &[u8] {
+        &self.bytes.0
+    }
+
     /// Returns the uniquely determined key with the given distance to `self`.
     ///
     /// This implements the following equivalence: