Verify payload gas limit against validator setting

[ckoopmann]

Currently we are not checking if the gas limit in the payload concurrs with the gas limit registered by the validator.

Special Case: If the requested gas limit is 0, validate the block as if it was 30 million (default)

[ckoopmann]

Reference implementation:

if registeredGasLimit == 0 && header.GasLimit == utils.CalcGasLimit(parent.GasLimit, 30_000_000) {
  // Prysm has a bug where it registers validators with a desired gas limit
  // of 0. Some builders treat these as desiring gas limit 30_000_000. As a
  // workaround, whenever the desired gas limit is 0, we accept both the
  // limit as calculated with a desired limit of 0, and builders which fall
  // back to calculating with the default 30_000_000.
} else {
  calculatedGasLimit := utils.CalcGasLimit(parent.GasLimit, registeredGasLimit)
  if calculatedGasLimit != header.GasLimit {
    return fmt.Errorf("incorrect gas limit set, expected: %d, got: %d", calculatedGasLimit, header.GasLimit)
  }
}