Visualize Filecoin State

[ZenGround0]

There is a new visualization tool landing in this PR.

The basic idea is that it generates an interactive graph of the filecoin chain state and the amount of data found in its different regions. It operates on the head of the given lotus repo's chain and walks through the amount of data found in a lightweight snapshot. If you import a snapshot into the repo without syncing then this visualization shows you exactly the contents of that snapshot.

Steps to run this visualization:

0. Initialize a lotus repo
1. Run ./lotus-shed --repo=~/.lotus stat-snapshot to output a json summary of different pieces of state. This JSON file is of the form { <path-to-state-region>, {"Size": <size-of-region-in-bytes>, "Links":<number-of-objects-in-dag>} ... }.
2. Run cat <json-file> | python3 scripts/snapshot-summary.py which will launch the interactive graph in a local browser instance.

Note the first command traverses all chain data and is therefore a long running process. On a mainnet node's repo it takes a little over 5 hours to run on a cloud instance with ~60GB of memory.