It had sequential async calls with complexity O(n), with a variety of redundant
calls. There was also a constant of... 4? 5? for each item. Now, the total
sequence depth is just 3-4.
Completes the `Executed` enum in the router. Adds an `Escape` struct. Both are
needed for testing purposes.
Documents the gas constants in intent and reasoning.
Adds modernized tests around key rotation and the escape hatch.
Also updates the rest of the codebase which had accumulated errors.
This technically has a TOCTOU where we sync an Epoch's metadata (signifying we
did sync to that point), then check if the Router was deployed, yet at that
very moment the node resets to genesis. By ensuring the Router is deployed, we
avoid this (and don't need to track the deployment block in-contract).
Also uses a JoinSet to sync the 32 blocks in parallel.
