necessary fixes for addNativeGas method

[canhtrinh]

• accept a multipler in the AddGasOptiosn
• take in the same gasLimit that was used in the first call for the tx (e.g. if estimateGasFee was originally invoked with 1mm gasLimit, then need to use 1mm gasLimit for addNativeGas)
• determine how much gas to add based on where the tx is:
  • if it has already been approved and execution attempted, sdk should return full execution fee
  • if it has not already been approved and execution not attempted, sdk should subtract gas already paid by user
  • if it has already been confirmed (i.e. by axelerons), then subtract the original base fee