fix: backwards compatibility for eth_feeHistory

[roynalnaruto]

Motivation

Geth v1.10.6 expects blockCount parameter in the RPC call to eth_feeHistory to be an unsigned integer, whereas since v1.10.7 it allows both unsigned integer as well as hex encoded uint. Hardhat allows only hex encoded uint.

The response format has also changed in Geth v1.10.7, whereby the field oldestBlock is now a hex-encoded uint.

Solution

Deserialisation of the FeeHistory struct is made backwards-compatible with Geth v1.10.6 as well, and in case the call to Hardhat (or any other client only supporting hex-encoded form for blockCount ) fails, we fallback to the unsigned integer serialiastion while making the RPC call.

Note: This is for convenience for more users since a few networks (at this point in time Infura) are running Geth v1.10.6, while others may have upgraded. We don't want the eth_feeHistory to fail, since the EIP-1559 fee estimator makes use of this RPC method.

[gakonst]

LGTM - one small nit if you want to make it slightly easier to use