feat: add support of the feemodel params.

[dzmitryhil]

Description

Integration of the feemodel modules params.

API Query examples

Example of the GraphQL request:

query MyQuery {
  feemodel_params {
    params
  }
}

Example of the GraphQL response:

{
  "data": {
    "feemodel_params": [
      {
        "params": {
          "model": {
            "max_discount": "0.123450000000000000",
            "max_block_gas": 50000000,
            "initial_gas_price": "0.062500000000000000",
            "long_ema_block_length": 1000,
            "short_ema_block_length": 10,
            "max_gas_price_multiplier": "1000.000000000000000000",
            "escalation_start_fraction": "0.800000000000000000"
          }
        }
      }
    ]
  }
}

---

This change is 

[miladz68]

Reviewed 22 of 22 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @silverspase, @wojtek-coreum, and @ysv)

[vertex451]

Very interesting

[ysv]

Reviewed 22 of 22 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @wojtek-coreum)