Header accumulator and the ability to validate blocks

[arnetheduck]

Looking at the header accumulator, it looks like it's accumulating block roots together with difficulty:

portal-network-specs/header-gossip-network.md

Line 13 in 6b06db1

## The "Header Accumulator"

In the beacon chain, a similar construct exists which accumulates [block_root, state_root], but we're currently in the process of switching over to accumulating blocks and states separately, so as to allow groups of blocks to be validated without knowing the state roots, as knowing state roots is a messy problem: see ethereum/consensus-specs#2649

It looks like the construct here might run into a similar issue: block roots are generally useful to verify on their own - it might be a good idea to look into designs that separate the two.

[pipermerriam]

I'm closing this as I believe this is no longer an issue. Rought (but not fully agreed upon) plan is to freeze a single copy of the master accumulator at the point of the merge and rely on the beacon chain light protocol for post merge blocks.