optimize first operators for frozen-sequence

Author: fembina

Sources/Falko.Common.Sequences/Sequences/FrozenSequence.Operator.First.cs

@@ -20,8 +20,14 @@ public T First(Func<T, bool> predicate)
     {
         ArgumentNullException.ThrowIfNull(predicate);
 
-        foreach (ref readonly var item in this)
+        scoped ref var itemsReference = ref MemoryMarshal.GetArrayDataReference(_items);
+
+        var itemsCount = _itemsCount;
+
+        for (var itemIndex = 0; itemIndex < itemsCount; itemIndex++)
         {
+            var item = Unsafe.Add(ref itemsReference, itemIndex);
+
             if (predicate(item)) return item;
         }