Add dynamic fees config

[StephenButtolph]

Why this should be merged

With the introduction of dynamic fees, we need to pass the different configs through the node to the P-chain.

How this works

Adds dynamic fee config similar to the static fee config.

How this was tested

On startup, node logs values as expected:

{
   "dynamicFeeConfig":{
      "weights":[
         1,
         1,
         1,
         1
      ],
      "maxGasCapacity":1000000,
      "maxGasPerSecond":1000,
      "targetGasPerSecond":500,
      "minGasPrice":1,
      "excessConversionConstant":1
   }
}