feemarket: non-determinism on block gas

[mmsqe]

System info: [Include Ethermint commit, operating system name, and other relevant details]

Steps to reproduce:

1. run make test-sim-nondeterminism with mmsqe@4d64b4b

Expected behavior: [--- PASS: TestAppStateDeterminism]

Actual behavior: [--- FAIL: TestAppStateDeterminism ]

__Additional info: block_gas brings the diff caused by random length memo, fixed memo length could bypass the test

[adu-web3]

the reason is easy:
https://github.com/mmsqe/cosmos-sdk/blob/dbe1dba5a6dfa118412a6a3ea795c5f1b746eee7/simapp/helpers/test_helpers.go#L26

r := rand.New(rand.NewSource(time.Now().UnixNano()))

GenTx is not using Simstate.Rand, so every time it creates memo with different length.
And ethermint.AnteHandler is consuming gas according to the tx bytes length, so finally gas used is not deterministic.

[mmsqe]

memo with rand seed works, this test "PASS" randomly before with larger NumBlocks, since we get blockSize 0 with gasWanted 0 based on matrix, which always compare same hash