This PR Adds:
* Backfilling routine, downloads and write to db all historical blocks.
* Prototype of first attempt at Database schema for Historical blocks.
* Fixed minor bugs.
* Support for following forks: Phase0, Altair, Bellatrix.
Embedded CL is not supported for Gnosis Chain, so it makes sense to set
`externalcl` to true by default for it.
Also, this PR sets `terminalTotalDifficultyPassed` for Gnosis Chain &
Chiado (see https://docs.gnosischain.com/updates/20221210-merge).
