feat: add validators voting data to db

[pdp2121]

High Level Overview of Change

On every most recent flag ledger, store for each validator into ballot table:

• ledger index - this will allow us to keep the most recent vote for a validator incase we missed the most recent flag ledger.

• fee voting

• amendment voting

This is to get amendment voting status and later fee votes.

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Tests (You added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation Updates
• [ ] Release

Future Tasks

• Add voting data to validators endpoint.
• Add a new amendments endpoint to returns amendments enabled on a network and voting data for pending ones.