Base: Replace average block time with average since last hour

[RiccardoM]

Currently BigDipper is showing the average time block since the genesis. Even though it might be interesting to show, this does not actually correspond to a valid block time that might be used inside computations. For example, let's consider the Desmos testnet and see what are the current averages.

Query

query AVBT {
  average_block_time_from_genesis {
    average_time
  }
  average_block_time_per_day {
    average_time
  }
  average_block_time_per_hour {
    average_time
  }
  average_block_time_per_minute {
    average_time
  }
}

{
  "data": {
    "average_block_time_from_genesis": [
      {
        "average_time": 5.8159952235726715
      }
    ],
    "average_block_time_per_day": [
      {
        "average_time": 5.670395760204752
      }
    ],
    "average_block_time_per_hour": [
      {
        "average_time": 5.679996694006309
      }
    ],
    "average_block_time_per_minute": [
      {
        "average_time": 5.649819909090909
      }
    ]
  }
}

As you can see, the average_block_time_from_genesis is around 5.81 seconds, while the other averages are all around 5.67 to 5.65 seconds. This is due to the fact that the average_block_time_from_genesis also considers all the chain halts that have happened. This way, the average block time will always be larger than the actual average, which might result in problems later on.

This is a problem for people that might use this value for some calculations (eg. estimated upgrade time) due to the fact that if a larger average time is considered, the upgrade will happen way before the time wanted. Considering an upgrade to happen in 30.860 blocks (~ 2 days considering a bloc time of 5.6 seconds), if the displayed average is 0.2 seconds larger (so it's 5.8 seconds), this means the upgrade will happen almost 2 hours before the estimated time. This actually happened inside our Desmos testnet.