Add callback for unpair_device (CON-1879)

[tomasmcguinness]

Description

Fixed #1605

This PR adds two new optional callbacks, which are invoked in response to the unpair_device function in the pairing_command

// Callback for the success of unpairing
void (*unpair_success_callback)(NodeId removed_node);
// Callback for the failure of unpairing
void (*unpair_failure_callback)(NodeId removed_node, CHIP_ERROR error);

Related

Testing

To test, I implemented the callback and performed an unpair_device operation. The logs show that the success case was handled.

When unpairing a node that doesn't exist, the on_unpair_failure_callback is also invoked successfully.

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Checklist

Before submitting a Pull Request, please ensure the following:

• [*] 🚨 This PR does not introduce breaking changes.
• [*] All CI checks (GH Actions) pass.
• [*] Documentation is updated as needed.
• [*] Tests are updated or added as necessary.
• [*] Code is well-commented, especially in complex areas.
• [*] Git history is clean — commits are squashed to the minimum necessary.

[wqx6]

May we add the unpair callback to the pairing_command_callbacks_t struct so that we can set the callbacks uniformly?

[tomasmcguinness]

May we add the unpair callback to the pairing_command_callbacks_t struct so that we can set the callbacks uniformly?

I took another look and found how to make it work with the existing callbacks.

I've updated the PR description.

This is a much neater solution. Thx.