Support featureXRPFees amendment

[ckniffen]

This amendment is part of [email protected] and updates the fees to be formatted as Amounts.

XRPLF/rippled#4247

• For server_info favor the following in order
  • reserve_base_drops, reserve_base, reserve_base_xrp
  • base_fee_drops, base_fee, base_fee_xrp
  • reserve_inc_drops, reserve_inc_fee, reserve_inc_fee_xrp
• If specifically looking for fees such as in the client libraries when autofilling use the command fee which is not changed by this PR and is already in drops.
• Validations processing will need to be handled similar to server_info.
• Fee property on all transactions remains the same
• SetFee transactions
  • BaseFeeDrops, ReserveBaseDrops, and ReserveIncrementDrops will be present when the amendment is passed and on new transactions. These will be of the type Amount
  • BaseFee, ReserveBase, ReferenceFeeUnits, ReserveIncrement are valid only historically after the amendment passes
  • No need for validation updates in client libraries as this is a pseudo transaction
  • Types should reflect there will be only one of the two sets of fields
• FeeSettings
  • New fields need to be added to the type.