Send device-preferred Thread dataset if different from core

[jpelgrom]

Summary

Expand the automatic Thread dataset sync on Matter commissioning to also send the device-preferred Thread dataset if it's different from core (it will either receive something new or update).

Thread datasets are now synced:

• If the device has a preferred dataset that doesn't match the server (because it has nothing or a different one), send the device dataset to the server
• If the device doesn't have a preferred dataset and the server does, add the server dataset to the device

Screenshots

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Link to pull request in Documentation repository

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Any other notes