Add option to store and retrieve deltas

## Status

Currently node stores a few deltas in memory only.

## Expected

Node optionally stores deltas along with blocks and allows for retrieval from storage.
This could be available only with PebbleDB compressed storage to not go beyond current full archival SQLite storage requirements.

Imagine a follower-less infra once dedicated archivers have this option enabled.

## Urgency

Alognode.io built a dedicated pipeline and a block server just for that - to solve the jittery nature of the current conduit/follower pipeline.

https://github.com/AlgoNode/blocksrv
https://github.com/AlgoNode/conduit-plugin-export-blksrv