* Testing Beacon API
* Fixed sentinel code (a little bit)
* Fixed sentinel tests
* Added historical state support
* Fixed state-related endpoints (i was drunk when writing them)
"whitelisting" mechanism (list of files - stored in DB) - which
protecting us from downloading new files after upgrade/downgrade was
broken. And seems it became over-complicated with time.
I replacing it by 1 persistent flag inside downloader:
"prohibit_new_downloads.lock"
Erigon will turn downloader into this mode after
downloading/verification of first snapshots.
```
//Corner cases:
// - Erigon generated file X with hash H1. User upgraded Erigon. New version has preverified file X with hash H2. Must ignore H2 (don't send to Downloader)
// - Erigon "download once": means restart/upgrade/downgrade must not download files (and will be fast)
// - After "download once" - Erigon will produce and seed new files
```
------
`downloader --seedbox` is never "prohibit new downloads"
* Most of the PR changed files are extra and slightly more complicated
unit tests.
* Fixed Eth1DataVotes not inheriting genesis
* Fixed Attestations simulation using wrong slot when reconstructing
partecipation
* Fixed Copy() operation on BeaconState on Eth1DataVotes
* Used correct ListSSZ type for Eth1DataVotes and HistoricalSummaries
* Fixed wrong []uint64 deltas on empty slots
What does this PR do:
* Optional Backfilling and Caplin Archive Node
* Create antiquary for historical states
* Fixed gaps of chain gap related to the Head of the chain and anchor of
the chain.
* Added basic reader object to Read the Historical state
