feat(polygon): remove dependency on gas station

[0xfourzerofour]

[Closes] #377

Proposed Changes

• Remove gas station code and calculate fees directly from eth_feeHistory rpc api.
• No need for ethers conversion code anymore as RPC returns in correct format without needing to multiply

[dancoombs]

This looks reasonable as a polygon fee estimation replacement. I think we should move towards this method for all of our fee estimation and be able to configure this via a CLI flag.

Maybe we get this merged to fix the polygon issue, and then file a ticket for a follow up that uses fee_history for all networks?

[dphilipson]

Looks really good! A few comments inline.

[dancoombs]

Before we merge this, can you do a quick spot check that when you run a local node from this branch and hit staging you get similar if not equal values for rundler_maxPriorityFeePerGas

LGTM though, nice work!

[dancoombs]

Also, don't for get to rebase to 1 commit!

[0xfourzerofour]

@dancoombs Yeh that is how I have been testing it. Checking gas station and comparing values. There is some slight differences but I think it is due to gas station delay