wl_keyboard: don't send key-up events for keys that are not logically down

src/utils/vecset.rs

@@ -19,7 +19,6 @@ impl<T> Deref for VecSet<T> {
 }
 
 impl<T> VecSet<T> {
-    #[expect(dead_code)]
     pub fn clear(&mut self) {
         self.vec.clear();
     }
@@ -47,4 +46,13 @@ impl<T: PartialEq> VecSet<T> {
     pub fn pop(&mut self) -> Option<T> {
         self.vec.pop()
     }
+
+    pub fn extend(&mut self, vals: &[T])
+    where
+        T: Copy,
+    {
+        for v in vals.iter().copied() {
+            self.insert(v);
+        }
+    }
 }