Add `HistoricalSummaries` to beacon chain network specs

[ogenev]

What was wrong?

We need a way to verify the canonicalness of post-merge execution block headers.

How was it fixed?

1. Define HistoricalSummaries data

• The BeaconState field historical_summaries (historical_roots before Capella) provides an ongoing accumulator for Merkle roots of recent history logs. We can use this accumulator (with proof against the state root) to verify canonicalness for execution block headers older than 8192 slots (~27 hours).

2. Move from the Beacon Chain Light Client Network narrative to the Beacon Chain Network, as not all of the data stored in the network is required by the light client protocol.

[ogenev]

I'm not too convinced yet about adding it in the Beacon Chain Light Client network and renaming that network to the Beacon Chain Network, as more objects from Beacon Chain are likely to be added,

Do you mean that we may want to have two separate networks - Beacon Chain Network and Beacon Chain Light Client network?

[kdeme]

Do you mean that we may want to have two separate networks - Beacon Chain Network and Beacon Chain Light Client network?

Yeah, but I realize it would be only 1 content type currently, so we could skip it for now.