Plotting metadata refactoring

[nazar-pc]

Two things changed here:

• sector metadata was sent twice unnecessarily before in the plotting result, so encoded duplicate was removed
• plotted sector as a whole was in the plotting progress notification, which was a problem if we were sending it across the network due to both large allocation necessary and awkwarness with data structure encoding that doesn't fit into NATS message size

With these changes implementation of farming cluster and similar use cases will be much easier and more memory-efficient.

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