[SERVICES-2651] Add extra fields to staking model

[mad2sm0key]

Reasoning

• expose values for staking APR and rewards remaining days if not capped by max APR

Proposed Changes

• add aprIfUncapped and rewardsRemainingDaysIfUncapped fields to Staking model
• add field resolvers and compute methods
• small refactor to remove duplicate code

How to test

query {
  filteredStakingFarms(filters: {}, pagination: { first: 200 }) {
    edges {
      node {
        address
        farmingToken {
          identifier
        }
        apr
        aprIfUncapped
        rewardsRemainingDays
        rewardsRemainingDaysIfUncapped
      }
    }
  }
}

[cfaur09]

Test done 🟢