Staking Router post-audit fixes

[Psirex]

Simple summary

The common changes in this commit are tests. But there are also a couple of changes in contracts: in the distribution of rewards bug has been fixed, a limit on the number of modules has been added, NodeOperatorRegistry contract has been modified to reduce the bytecode size, and external methods use uint256 data instead uint24 if applicable.

Contracts Changes

• Lido.sol

  • added Lido.getVersion() method

• StakingRouter.sol

  • added stakingModules limit
  • changed uint24 _stakingModuleId -> uint256_stakingModuleId, add lenght check + cast for external functions
  • fix getStakingRewardsDistribution() rewarded modules collection
  • stricter naming convention module -> stakingModule across the code
  • added getVersion() method
  • changed visibility of FEE_PRECISION_POINTS constant
  • unified events params and their sequence

• NodeOperatorsRegistry.sol

  • fix wrong vetted keys calculation on finalizeUpgrade_v2() for deactivated node operators
  • remove extra check that _exitedValidatorsKeysCount >= 0 from unsafeUpdateExitedValidatorsKeysCount()
  • remove NodeOperatorUnusedValidatorsKeysTrimmed emitting from the invalidateReadyToDepositKeys() and fix the wrong totalKeysTrimmed argument value in the NodeOperatorTotalKeysTrimmed event
  • rework removeSigningKey() to used _removeUnusedSigningKeys() under the hood
  • rework removeSigningKeyOperatorBH() to used _removeUnusedSigningKeys() under the hood
  • move onlyExistedNodeOperator(_nodeOperatorId) check to the _removeUnusedSigningKeys() method
  • get rid of repeated checks and events emitting in the _removeUnusedSigningKey() by moving them into the _removeUnusedSigningKeys()
  • add getStETH() method
  • The next modifications were applied to the NodeOperatorsRegistry contract to reduce the bytecode size from 27.511 Kb to 23.507 Kb:
    • Replace modifiers with internal methods
    • Refactor updateExitedValidatorsKeysCount() & unsafeUpdateExitedValidatorsKeysCount() to use the same internal method _updateExitedValidatorsKeysCount()
    • Refactor addSigningKeys(), addSigningKeysOperatorBH() to use the same internal method _addSigningKeys()
    • Refactor removeSigningKey(), removeSigningKeys(), removeSigningKeyOperatorBH(), and removeSigningKeysOperatorBH() to use the same internal method _removeUnusedSigningKeys()

Tests

• Added Lido.sol tests and coverage
  • 100% Statements 179/179
  • 98.57% Branches 69/70
  • 100% Functions 52/52
  • 100% Lines 179/179
• 100% coverage by unit tests for the NodeOperatorsRegistry contract.
• MinFirstAllocationStrategy.sol tests for solidity version 0.4.24
• Added a 3000+ test cases for StakingRouter.getKeysAllocation()