TIP-33: Staking contract upgrade

In this proposal, we present a reduced set of changes to the staking contract that improve the gas efficiency, the clarity and the user experience of the staking protocol. See the full description of the proposal and associated discussion here:

https://forum.threshold.network/t/tip-33-staking-contract-upgrade

New implementation contract with the proposed changes can be found here:

https://etherscan.io/address/0x57e1a87603bd1960d734243f8b2f5133911e009d