Refactor witness-accumulation in EVM (#42)

* make push dynamically-charged.  charge witness gas costs for push.  refactor evm witness gas charging to move logic for touching a range of bytecode into a helper method 'touchEachChunksAndChargeGas'

* add witness gas calculation for CodeCopy, ExtCodeCopy, SLoad back to gas_table.go

* witness gas charging for CALL

* remove explicit reference to evm.TxContext

* core/vm: make touchEachChunksAndCharge gas handle nil code value

* core/vm: call implementation, separate out witnesses into touch/set

* some fixes

* remove witness touching from opCall: this will go in evm.go

* remove witness touching for call from gas_table.go

* (hopefully) fix tests

* add SSTORE witness charging that was removed mistakenly

* charge witness gas for call

* clean up and comment touchEachChunksAndChargeGas

* make suggested changes

* address remaining points

* fix build issues

* remove double-charging for contract creation witness gas charging

core/state_processor.go

@@ -128,7 +128,9 @@ func applyTransaction(msg types.Message, config *params.ChainConfig, bc ChainCon
 		receipt.ContractAddress = crypto.CreateAddress(evm.TxContext.Origin, tx.Nonce())
 	}
 
-	statedb.Witness().Merge(txContext.Accesses)
+	if config.IsCancun(blockNumber) {
+		statedb.Witness().Merge(txContext.Accesses)
+	}
 
 	// Set the receipt logs and create the bloom filter.
 	receipt.Logs = statedb.GetLogs(tx.Hash(), blockHash)