Set `maxSafeGasPrice` depending on network_id

[davidyuk]

aepp-sdk-js/src/tx/builder/field-types/gas-price.ts

Line 22 in 2f3c8cb

const maxSafeGasPrice = BigInt(MIN_GAS_PRICE) * 100000n; // max microblock fee is 600ae or 35usd

Currently, it is bonded to aeternity mainnet. Maybe the whole gas price increase calculation should be implemented differently, depending on the network id.