Decouple the block reward logic and make it configurable

[adlrocha]

We currently use a flat reward logic in Eudico, where the validator that signs the block gets the full reward:

eudico/chain/consensus/common/executor.go

Line 222 in b85d68f

func applyMiningRewards(ctx context.Context, vmi vm.Interface, em stmgr.ExecMonitor, b store.BlockMessages, epoch abi.ChainEpoch, ts *types.TipSet, value abi.TokenAmount) error {

This makes sense for longest-chain protocols, but in other consensus algorithms (like BFT) where the block validation is "collaborative", we should support other reward strategies. Having a configurable block reward also enables subnets to choose the incentive system that better suits them.

I propose to implement an interface for the block reward, and pass the desired reward scheme as an argument in subnets and consensus algorithms.