ethexe: reward commitments

[grishasobol]

Problem to Solve

Rewards are not implemented and designed yet. But we could start to work with reward commitment support.

Possible Solution

Symbiotic has two different types of rewards:

1. Staker rewards - distributor (for example router or middleware) just send reward to vault which would decide distribution for stakers.
2. Operator rewards - works thru merkle tree proof.

What we should do in MIddleware.sol:

1. append refs to both rewards services, see https://github.com/symbioticfi/rewards.
2. create interface to distribute rewards (which will be used by router)

What we should do in Router.sol:

1. append commitment

CommitRewards {
       rewards_to_vaults: Vec<(address, u256)>,
       operators_reward_tree_root: H256,
}

2. create interface to apply this commitment

What we should do in validators:

1. Support possiblity to submit reward commitment.
2. support of storing operators rewards as merkle tree in db. For claiming operator has to provide merkle tree proof for reward service that it really has been granted to claim the reward.

Notes

No response