replace MessageRunMode with a struct

[magicxyyz]

This PR:

• replaces MessageRunMode enum with MessageRunContext struct, that apart from run mode now contains wasm cache tag and wasm targets list
• Refactors passing of wasm targets and wasm cache tag, so they are no longer wired through cachingDB and ethdb.Database

Resolves NIT-2827

[tsahee]

flagging this TODO question

[tsahee]

@PlasmaPower it seems that here we set it to GasEstimationMode because in the function runScheduledTxes (just below this one) we only run scheduled Txes for gas estimation mode.. but I don't understand that condition itself (currently, we call runScheduledTxes from two places I found, both set runmode argument to GasEstimation so this condition isn't really doing anything)

[magicxyyz]

runScheduledTxes was added in: 018bd54

it addressed following comment: #304 (comment)

this is how it looked like before:

go-ethereum/internal/ethapi/api.go

Lines 1131 to 1170 in 9830725

	// Arbitrum: a tx can schedule another (see retryables)
	scheduled := result.ScheduledTxes
	for runMode == core.MessageGasEstimationMode && len(scheduled) > 0 {
	// This will panic if the scheduled tx is signed, but we only schedule unsigned ones
	msg, err := core.TransactionToMessage(scheduled[0], types.NewArbitrumSigner(nil), header.BaseFee)
	if err != nil {
	return nil, err
	}
	// The scheduling transaction will "use" all of the gas available to it,
	// but it's really just passing it on to the scheduled tx, so we subtract it out here.
	if result.UsedGas >= msg.GasLimit {
	result.UsedGas -= msg.GasLimit
	} else {
	log.Warn("Scheduling tx used less gas than scheduled tx has available", "usedGas", result.UsedGas, "scheduledGas", msg.GasLimit)
	result.UsedGas = 0
	}
	msg.TxRunMode = runMode
	// make a new EVM for the scheduled Tx (an EVM must never be reused)
	evm := b.GetEVM(ctx, msg, state, header, &vm.Config{NoBaseFee: true}, &blockCtx)
	go func() {
	<-ctx.Done()
	evm.Cancel()
	}()
	scheduledTxResult, err := core.ApplyMessage(evm, msg, gp)
	if err != nil {
	return nil, err // Bail out
	}
	if err := state.Error(); err != nil {
	return nil, err
	}
	if scheduledTxResult.Failed() {
	return scheduledTxResult, nil
	}
	// Add back in any gas used by the scheduled transaction.
	result.UsedGas += scheduledTxResult.UsedGas
	scheduled = append(scheduled[1:], scheduledTxResult.ScheduledTxes...)
	}
	return result, nil

[magicxyyz]

so I think we need to just pass runCtx here, instead of overwriting it with gas estimation context

[tsahee]

we always need loclaTarget.
Maybe make the argument extraWasmTargets, and then the function adds local if not already in there, and in most invocations you can just pass nil?

[tsahee]

another option is to special case len(wasmTargets) == 0 and in that case add localTarget

[magicxyyz]

went with the second option, if len(wasmTargets) == 0 then wasmTargets = [localTarget]