[Lake] Hook up slots + bronze_slots table

[idiom-bytes]

Motivation

Many dashboards may require a clean, up-to-date slots table.

This is the 2nd base table in predictoor to provide analytics.
Below are the e2e steps to get bronze_pdr_slots data implemented with the current system.

DoD

• subgraph_slot.py already implements a get_slot() to fetch latest slots.
• subgraph object needs to be created
• subgraph mock objects and fixtures
• lake/table_pdr_slot.py needs to be created
• schema for dfs needs to be created
• hooks for gql_data_factory.py
• hooks for bronze_pdr_slots.py
• logic for bronze_pdr_slots.py to join data from [slots, predictions, truevals, and payouts]
• tests and coverage

[idiom-bytes]

We want properties from all 4 tables:

1. slots (info about the slot, feed, etc..)
2. predictions (all predictions submitted and their final results)
3. truevals (what was the final result)
4. payouts (gives you total revenue, and payout of individuals)

I'll try to expand the following...

{
  predictSlots(last:1000, next: 15000) {
    id
    slot
    roundSumStakesUp
    roundSumStakes
    predictions {
      id
      user {
        id
      }
      stake
    }
    revenue
    revenues {
      id
      amount
    }
  }
}