[SYCL][NFC] Add user-defined destructor and assignment operator

[uditagarwal97]

Coverity suggested to add these to follow the rule-of-three (https://en.cppreference.com/w/cpp/language/rule_of_three.html)

[Copilot]

Pull Request Overview

This PR addresses a Coverity warning by explicitly defining special member functions to adhere to the C++ rule-of-three.

• Adds a user-defined destructor to node_impl
• Deletes the copy assignment operator in graph_mem_pool
• Ensures graph_mem_pool cannot be copied or assigned

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
sycl/source/detail/graph/node_impl.hpp	Introduces an empty destructor to follow rule-of-three
sycl/source/detail/graph/memory_pool.hpp	Deletes the copy assignment operator for the memory pool

Comments suppressed due to low confidence (1)

sycl/source/detail/graph/node_impl.hpp:187

• Defining an empty destructor suppresses the implicitly generated move operations and isn’t necessary here; consider using ~node_impl() = default; or omitting it entirely.

  ~node_impl() {}

[Copilot]

According to the rule-of-three, if you define a destructor, you should also explicitly define or delete the copy constructor and copy assignment operator; consider adding or deleting those to avoid accidental copying.

[uditagarwal97]

We already have copy constructor and assignment operator defined.

[Copilot]

The copy constructor deletion uses a non-const reference, but the default copy constructor signature takes a const reference. As a result, the class remains copyable; change it to graph_mem_pool(const graph_mem_pool&) = delete;.

Suggested change

	graph_mem_pool(graph_mem_pool &) = delete;
	graph_mem_pool(const graph_mem_pool &) = delete;

[uditagarwal97]

That's orthogonal to the changes in this PR.