Fix/enable Shanghai fork

[roman-khimov]

We don't have https://github.com/ethereum/execution-specs/blob/master/network-upgrades/mainnet-upgrades/shanghai.md enabled in our configs which makes us incompatible with the most recent Solidity tools producing PUSH0 (likely other problems can happen as well). Enabling it breaks dbft though (as well as clique), so this requires some fixes from the consensus part.

Refs. #110.

[AnnaShaleva]

From the brief glance Shanghai is not supported in the Clique because of https://eips.ethereum.org/EIPS/eip-3651 and because of the fact that in Clique Coinbase should be empty on checkpoint blocks. In dBFT we don't have checkpoint blocks and don't have such problem (Coinbase is always set in dBFT), thus I'd say we should allow Shanghai support in dBFT.

But it needs additional investigation, https://eips.ethereum.org/EIPS/eip-4895 also may be related.

[AnnaShaleva]

According to the post-merge Beacon consensus code, WithdrawalsHash block field is also affected by Shanghai:

go-ethereum/consensus/beacon/consensus.go

Lines 265 to 271 in df01fe2

	shanghai := chain.Config().IsShanghai(header.Number, header.Time)
	if shanghai && header.WithdrawalsHash == nil {
	return errors.New("missing withdrawalsHash")
	}
	if !shanghai && header.WithdrawalsHash != nil {
	return fmt.Errorf("invalid withdrawalsHash: have %x, expected nil", header.WithdrawalsHash)
	}