Gloas: cold DB

[michaelsproul]

Description

I've implemented all the hot DB changes required for Gloas in this PR:

• Update database and block replayer to handle payload envelopes #8886

This issue tracks the implementation for the cold DB. I think we can get by without a schema change initially (similar to hot DB), but may want one before going live on mainnet.

[michaelsproul]

Totally fine now that we have merged:

• Gloas spec v1.7.0-alpha.5 and beacon_chain tests #8998