fix(eip1559): use hex number for eth_feehistory 'blockcount' parameter

[alexandre-abrioux]

🚨 rainbow-me/fee-suggestions#25 is needed before merging this PR.

Description of the changes

Quicknode's RPC servers do not allow the use of an integer for the blockCount argument of eth_feeHistory.
Indeed, the doc specifies that it should be an hexadecimal number:
https://infura.io/docs/ethereum#operation/eth_feeHistory
Infura and Alchemy are more permissive in this regard.

This change will use the hex string instead of an integer to check if eth_feeHistory is supported on the RPC backend.

We need to wait for an update of the rainbow-me/fee-suggestions library before merging this because this library is using an integer and not a hex string in its RPC calls. If we merged this PR right away we would generate errors when running the request-node against Quicknode's backend.

[bertux]

So why not switch first to Alchemy RPC ?

[alexandre-abrioux]

@bertux Infura & Alchemy do not support the Gnosis Chain.
But this PR is not urgent since the original issue was that we were not calling the GasPriceDefiner in TheGraphStorage, so we were using a gas price that was too low sometimes, and this was fixed in #760.

[alexandre-abrioux]

Marking this as Draft, PR is stale

[alexandre-abrioux]

rebased to fix conflicts following refactor in #931

[coveralls]

Coverage: 87.784%. Remained the same when pulling d01e8fe on fee-history-hex into 35f2ede on master.

[alexandre-abrioux]

rainbow-me/fee-suggestions#25 has been merged, and the lib has been updated by @leoslr in #1072, merging this now