kaiax/staking: Add StakingModule

[blukat29]

Proposed changes

This PR is merging a subset of feat/kaiax branch into dev branch. This PR Adds the kaiax/staking module. See kaiax/staking/README.

• Add the implementation
• Register to:
  • CN as BaseModule
  • CN as JsonRpcModule (for kaia_getStakingInfo and governance_getStakingInfo)
  • BlockChain as RewindableModule
  • IstanbulBackend as StakingModule (to pass it to weightedCouncil and reward_distributor) -- this use case will be removed once we introduce kaiax/valset and kaiax/reward.

Next PR:

• Replace existing usages of staking_manager.go
  • weightedCouncil
  • p2p stakinginfo handler
  • unit tests
• Implement "Preload" logic in kaiax/staking.

Types of changes

• [ ] Bugfix
• [x] New feature or enhancement
• [ ] Others

Checklist

• [x] I have read the CONTRIBUTING GUIDELINES doc
• [x] I have read the CLA and signed by comment I have read the CLA Document and I hereby sign the CLA in first time contribute
• [ ] Lint and unit tests pass locally with my changes ($ make test)
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation (if appropriate)
• [ ] Any dependent changes have been merged and published in downstream modules

Related issues

Further comments