Enable efficient fetching of latest version of the document

[lucasvo]

Given the following scenario:

Doc1:
Node A: v0 | v1 | v2 | v3
Node B: v0 |    |    | ?

When B requests the latest versions (only from a version onwards) from A, A:

• Gather all versions that B has access to, with all data within. As this will be needed as well by the signature state consensus issue.
• Send them to B

Then B:

• Stores versions
• For latest one, add entry to new table document_latest that points to latest document version
• In case that B has missing access to a version of the document, then fill with headers-only and overridable block version. (debatable if needed)

Changes:

• New p2p endpoint that returns all versions that a collaborator has access to, given a start version:

{
    DocIdentifier: docID,
    FromNonce: fromNonce,
}

• Add Simple Index table to find latest document versions.
  • Every new document update need to update the latest version value
• Remove logic to iterate over versions (search) to find the latest on GetLatestDocumentVersion, just access the latest document table