Darwin Matter.framework should not call back into client code while on the Matter queue

[bzbarsky-apple]

Some of the Darwin APIs do sync dispatch to the Matter queue. That means we must never call out to consumers while on the Matter queue; otherwise we can deadlock.

This is definitely a problem for MTRDeviceAttestationDelegateBridge but also likely for other @protocol bits that are expected to be implemented by consumers. We need to carefully audit all of these and figure out how to call them on non-Matter queues, or at least document the restrictions on what can be done inside the callbacks.

[bzbarsky-apple]

Going through our current @protocol implementations:

• MTRStorage: has to be sync-called from the Matter queue, but we do it via another dispatch queue to serialize the storage access.
• MTROTAProviderDelegate: Now called async on its own queue, so not an issue.
• MTRDeviceDelegate: Called async on the caller-provided queue.
• MTRDeviceAttestationDelegate: Called async, but on the Matter queue. Needs to be fixed to use its own per-bridge queue.
• MTRDeviceControllerServerProtocol and MTRDeviceControllerClientProtocol: no idea
• MTRDeviceControllerDelegate/MTRDevicePairingDelegate: Called async on the caller-provided queue.
• MTRKeypair: has to be sync-called from the Matter queue.
• MTRNOCChainIssuer: Called on the consumer-provided queue.

So we just need to fix MTRDeviceAttestationDelegate.