Review sync committee rewards + penalties as PR 2453

[barnabemonnot]

This addresses recent changes in the eth2 specs relative to the sync committee rewards and penalties (PR#2453). Some changes:

• Review the incentive coefficients SYNC_COMMITTEE_WEIGHT and other *_WEIGHT
• Fix an issue with the sync committee reward computation in model/parts/incentives.py:

total_base_rewards = base_reward * number_of_validators

instead of

total_base_rewards = base_reward * number_of_validators_online

• Separate penalties incurred from attestation duties and sync committee duties, in a new partial state update block
• Review test checking whether rewards on a perfect network match the expected weights

[BenSchZA]

Made a few minor updates. Really appreciate the attention to detail!