Handle case when Etherscan EIP-1559 gas oracle is down

[onyb]

Do not prevent transaction creation when Etherscan's EIP-1559 gas oracle is down. Currently in such an event, we prevent creation of the unapproved transaction with the following error in the console:

Sending unapproved transaction failed: from=0xa92... err=Failed to get the gas fees for EIP-1559 transaction

There are several ways of addressing this. Here are some ideas:

• create a legacy Type-0 transaction instead.
• populate some sane defaults for maxPriorityFeePerGas and maxFeePerGas and hope there's enough room to burn the necessary base fee.

[aman-m1]

@onyb Any uodate here. I'm facing similar issue on zkSync Testnet and Mainnet- https://community.brave.com/t/swap-on-zksync-testnet-through-a-dapp-does-not-initiate/477412

[MicahZoltu]

An oracle isn't needed at all. Just set the maxFeePerGas to latestBlock.baseFee * 2 + 100000000 and set the maxPriorityFee to 100000000 (100000000 == 0.1 nanoeth).

That strategy should be used broadly, I don't know why you query an oracle at all.