docs: Fix memory module documentation discrepancies

- Add missing PoolAllocator class overview with methods table
- Add missing LinearAllocator class overview with methods table
- Add missing ProxyAllocator class overview with methods table
- Fix PoolAllocator::Allocate example code and comments
- Clarify ProxyAllocator::Free totalFreed calculation behavior
- Fix CreateLinearAllocator complexity from O(size) to O(1)
- Add note about Reallocate thread safety in ProxyAllocator

docs/api/memory/manager/create-linear-allocator.md

@@ -11,7 +11,7 @@ std::unique_ptr<LinearAllocator> CreateLinearAllocator(size_t size);
 
 **返回：** LinearAllocator 的 unique_ptr
 
-**复杂度：** O(size)
+**复杂度：** O(1)
 
 **示例：**