avoid unnecessary binary search in gas estimation

[shunjizhan]

Change

Currently the eth_estimateGas RPC is slow with a p95 performance of 3.5s. This is because we need to binary search the best passing gasLimit, which calls eth_call repeatedly, usually 5-8 times.

However, in most cases if the contract doesn't have special logics to deal with gas, a gasLimit that is slightly more than gasUsed should make it work. We only need to do binary search if that's not the case.

So we can first check if usedGas * 1.2 works, to avoid binary search in most cases, which should speed up the gas estimation, and respectively reduce node burden, by 5-8X .

Also removed some gas related legacy codes

Test

Added tests to make sure it still works for odd gas contract whose passing gaslimit is much higher than actual used gas