utils: uuid: define appending_hash<utils::tagged_uuid<Tag>>

And simplify usage for appending_hash<counter_shard_view>
respectively.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>

counters.hh

@@ -372,7 +372,7 @@ template<>
 struct appending_hash<counter_shard_view> {
     template<typename Hasher>
     void operator()(Hasher& h, const counter_shard_view& cshard) const {
-        ::feed_hash(h, cshard.id().uuid());
+        ::feed_hash(h, cshard.id());
         ::feed_hash(h, cshard.value());
         ::feed_hash(h, cshard.logical_clock());
     }

utils/UUID.hh

@@ -250,6 +250,14 @@ struct appending_hash<utils::UUID> {
     }
 };
 
+template<typename Tag>
+struct appending_hash<utils::tagged_uuid<Tag>> {
+    template<typename Hasher>
+    void operator()(Hasher& h, const utils::tagged_uuid<Tag>& id) const noexcept {
+        appending_hash<utils::UUID>{}(h, id.uuid());
+    }
+};
+
 namespace std {
 template<>
 struct hash<utils::UUID> {