Exponential rebates: deployment plan

For details on the upgrade see: GIP

We are doing this upgrade in two steps:

Step 1 (Stage 0 —> Stage 1): we change the channelDisputeEpochs value to 1 epoch
Step 2 (Stage 2 —> Stage 3): we upgrade the Staking, StakingExtension and RewardsManager contracts

The rationale for doing this in two stages can be found in the Backwards Compatibility + Upgrade Path section of the GIP.