[SERVICES-2436] Filtered staking farms query

[mad2sm0key]

Reasoning

• provide a Relay-compliant query for fetching staking farms data

Proposed Changes

• create new filteredStakingFarms query that follows the GraphQL "Connections" specification
• add staking farms filtering service (allows wildcard filtering by a token - needed for quick search)
• add method for computing a staking contracts deployedAt date (using API service)
• add sorting by farming token price, TVL, APR and deployment date

How to test

query {
  filteredStakingFarms(
    filters:{
      searchToken:"UTK"
    }
    pagination:{
      first:200
    }
    sorting: {
      sortField: TVL
      sortOrder:DESC
    }
  ) {
    edges {
      cursor
      node {
        address
        apr
        state
        farmTokenSupply
        farmingToken {
          identifier
          price
          supply
        }
        farmToken {
          ticker
        }
      }
    }
    pageInfo {
      startCursor
      endCursor
    }
    pageData {
      count
      limit
      offset
    }
  }
}