docs: Fix containers module documentation discrepancies

- Array::SetAllocator: Remove reference to non-existent PoolAllocator class
- HashMap::SetAllocator: Remove reference to non-existent GetDefaultAllocator()
- HashMap::Copy/Move: Fix move constructor complexity (O(m_bucketCount), not O(1))
- HashMap::iterator: Remove C++20 structured bindings example
- String: Add missing links for operator+ and operator==/!=

docs/api/containers/array/setallocator.md

@@ -27,7 +27,7 @@ auto* linear = new Memory::LinearAllocator(1024 * 1024);
 Containers::Array<int> arr;
 arr.SetAllocator(linear);
 
-// 使用内存池分配器
+// 使用对象池分配器
 auto* pool = new Memory::PoolAllocator(sizeof(MyObject), 100);
 Containers::Array<MyObject> objects;
 objects.SetAllocator(pool);