- Added tests covering Enumerator. (#164)

- Removed constructor which made it easy to read out of the valid span range.
  - Only used in one place, fixed that call site.

src/Arch/Core/Archetype.cs

@@ -404,7 +404,7 @@ internal void SetRange<T>(in Slot from, in Slot to, in T? component = default)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public Enumerator<Chunk> GetEnumerator()
     {
-        return new Enumerator<Chunk>(Chunks.AsSpan(), Size);
+        return new Enumerator<Chunk>(Chunks.AsSpan(0, Size));
     }
 
     /// <summary>

src/Arch/Core/Enumerators.cs

@@ -39,22 +39,6 @@ public Enumerator(Span<T> span)
         _index = _length;
     }
 
-    /// <summary>
-    ///     Initializes a new instance of the <see cref="Enumerator{T}"/> struct.
-    /// </summary>
-    /// <param name="span">The <see cref="Span{T}"/> with items to iterate over.</param>
-    /// <param name="length">Its length or size.</param>
-    public Enumerator(Span<T> span, int length)
-    {
-#if NET7_0_OR_GREATER
-        _ptr = ref MemoryMarshal.GetReference(span);
-#else
-        _ptr = new Ref<T>(ref span.DangerousGetReference());
-#endif
-        _length = length;
-        _index = _length;
-    }
-
     /// <summary>
     ///     Moves to the next item.
     /// </summary>