[TESTING] - `build_vid_proposal` should return all `VidDisperseShare`s

[lukaszrzasik]

What is this task and why do we need to work on it?

Currently build_vid_proposal arbitrarily returns the first VidDisperseShare proposal. It should return all the VidDisperseShares proposals so that the caller can decide which share it needs. Preferably VidDisperseShares proposals should be returned as a map: share recipient -> proposal.

What work will need to be done to complete this task?

No response

Are there any other details to include?

No response

What are the acceptance criteria to close this issue?

build_vid_proposal returns, e.g. HashMap<<TYPES as NodeType>::SignatureKey, Proposal<TYPES, VidDisperseShare<TYPES>>>

Branch work will be merged to (if not the default branch)

No response