Use a randomly constructed expander graph to select silos to probe

[ReubenBond]

See this thread for context + a code example from the RAPID repo: https://bsky.app/profile/rbn.bsky.social/post/3las2u6j6mk2q

Expander graphs improve fault detector coverage by reducing the chance that a set of silos which fail were largely monitoring each other. Without an expander graph, if silos A, B, C, D are next to each other in a ring of (eg 8 silos), then the failure of A, B, C means no silo is monitoring D, 1 silo monitors C, 2 silos monitor B, etc. This slows down the time to recover since A must be evicted before the failures of C & D can be detected.