shrexnd: requesting data and/or proofs for multiple namespaces

[Wondertan]

Overview

The goal is to extend the protocol to enable requesting multiple data and/or data proofs in one request. The current state of the protocol allows fetching all the data within a certain namespace but not within multiple.

Motivation

This is solely a networking optimization for Get method of BlobModule which otherwise would require sending multiple concurrent requests instead of one. In response, this would allow sending fewer proofs if data from different namespaces happens to be on the same EDS row.

Details

The protobuf has to be updated to an array of namespaces instead of a single one. Subsequently, the response will need to be updated to reflect that and keep multiple namespaced data entries with proofs. Additionally, the subtask is to investigate NMT multi-proof API to avoid proof duplicates shared between different namespaces.

[distractedm1nd]

Is this really necessary?

[Wondertan]

I see value in this optimisation long-term. Especially since Rollups want to use multiple namespaces or their block, e.g. one for headers and one for blocks. Anyway, does not hurt to keep an issue

[vgonkivs]

Close until we will need it