SnapSync algorithm design

[stranger80]

Use all content on SnapSync (clips, slides, quick-and-dirty implementation) to put down a high-level SnapSync algorithm specification in pseudo code or sequence/flow diagrams.

This should be the baseline for identification of alternative flows, failure scenarios, edge cases, etc. and be a spec for actual implementation.

[pnowosie]

Draft of the design can be found here
https://www.notion.so/nethermind/Snapsync-algorithm-design-c55065c45ed342c2be6d57dea6edac84