the memory strategy is holding owning references to the underlying C rcl handles (shared pointer of rcl_service_t / rcl_subscription_t etc).
those shared_ptrs keep the rcl entities alive past the lifetime of the Node (which un-initializes the rcl_node implementation).
when the rcl service/subscription is finally destroyed, rcl tries to access the node implementation which is already invalid
this generates the error messages during this test.

the objective with those tests are not lifetime of endpoint objects against the node.
these tests basically check if memory strategy APIs work okay with each endpoint.

Pull Request Overview

Purpose: Ensure test cases manually clear memory strategy handles before node destruction to avoid accessing destroyed nodes via weak pointers and prevent potential cleanup issues.
Key changes:

• Added calls to memory_strategy()->clear_handles() inside multiple test scopes.
• Added client_handle.reset() in get_client_by_handle test to prevent deleter accessing node.
• Inserted identical explanatory comments about clearing handles before node destruction.

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