Switch from using gasPrice to EIP-1559 fee model (maxFeePerGas / maxPriorityFeePerGas)

[Dzeranov]

Description

Currently, in transactions we are using the legacy gasPrice field for transaction fees. To align with the EIP-1559 fee model we should migrate all fee logic to utilize maxFeePerGas and maxPriorityFeePerGas instead.

EIP-1559 ref: https://eips.ethereum.org/EIPS/eip-1559