Persistence implementation incomplete

[koalatux]

It looks like the persistance implementation is at least in the light_eth example not complete. Storing seems to work when this line is changed, but loading is not implemented. Persistence works in the onoff_light example of rs-matter.

[ivmarkov]

Yes, unfortunately. I'm neck deep into implementing memory optimizations and some commissioning-related improvements to the underlying rs-matter. I hope in a month or so to be able to get back to this.

In the meantime, you could try to fix it and open a PR.