Produce and cache light client data in the BeaconChain to support fast gossip validation and RPC processing #4926
Description
Description
Our initial (& current) light client server implementation produces light client data on demand and is very expensive. It was a step in the right direction, but we need to be able to serve the data cheaply before the light client server can be enabled by default. @dapplion has been looking into this and suggested implementing a progressive message producer and caching strategy.