Simplify mock contract keeper processCallback logic

[colin-axner]

Summary

The current function uses the inputted gas amount for a transaction to perform actions for testing:

// processMockCallback returns nil if the gas meter has greater than or equal to 500000 gas remaining.
// This function consumes 500000 gas, or the remaining gas if less than 500000.
// This function oog panics if the gas remaining is less than 400000.
func (k ContractKeeper) processMockCallback(
	ctx sdk.Context,
	callbackType callbacktypes.CallbackType,
	authAddress string,
) error {
	gasRemaining := ctx.GasMeter().GasRemaining()

	// increment stateful entries, if the callbacks module handler
	// reverts state, we can check by querying for the counter
	// currently stored.
	k.IncrementStateEntryCounter(ctx)

	// increment callback execution attempts
	k.Counters[callbackType]++

	if gasRemaining < 400000 {
		// consume gas will panic since we attempt to consume 500_000 gas, for tests
		ctx.GasMeter().ConsumeGas(500000, fmt.Sprintf("mock %s callback panic", callbackType))
	} else if gasRemaining < 500000 {
		ctx.GasMeter().ConsumeGas(gasRemaining, fmt.Sprintf("mock %s callback failure", callbackType))
		return MockApplicationCallbackError
	}

	if authAddress == MockCallbackUnauthorizedAddress {
		ctx.GasMeter().ConsumeGas(500000, fmt.Sprintf("mock %s callback unauthorized", callbackType))
		return MockApplicationCallbackError
	}

	ctx.GasMeter().ConsumeGas(500000, fmt.Sprintf("mock %s callback success", callbackType))
	return nil
}

This can be hard to maintain since changing the gas for a transaction will change the expected output.

We could alternatively use the callback address to decide what the mock callback should do:

// processMockCallback returns nil if the gas meter has greater than or equal to 500000 gas remaining.
// This function consumes 500000 gas, or the remaining gas if less than 500000.
// This function oog panics if the gas remaining is less than 400000.
func (k ContractKeeper) processMockCallback(
    ctx sdk.Context,
    callbackType callbacktypes.CallbackType,
    contractAddress string,
) error {
    gasRemaining := ctx.GasMeter().GasRemaining()

    // increment stateful entries, if the callbacks module handler
    // reverts state, we can check by querying for the counter
    // currently stored.
    k.IncrementStateEntryCounter(ctx)

    // increment callback execution attempts
    k.Counters[callbackType]++

    // consume a single gas to indicate gas consumption occurred
    ctx.GasMeter().ConsumeGas(1, fmt.Sprintf("mock %s callback panic", callbackType))

    switch contractAddress {
    case PanicContract:
        ctx.GasMeter().ConsumeGas(gasRemaining+1, fmt.Sprintf("mock %s callback panic", callbackType))
    case UnauthorizedContract, FailureContract:
        return MockApplicationCallbackError
    case SuccessContract:
        return nil 
    }   

    return nil
}

with

const (
    UnauthorizedContract = "unauthorized"
    PanicContract        = "panics out of gas"
    FailureContract      = "failure"
    SuccessContract      = "success"
)   

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[colin-axner]

If we do this, we can add test cases in the integration for using a FailureContract, I've removed the cases which tried executing a failure via a certain gas amount. It was too difficult to assert the contract failed in those cases

[colin-axner]

When this issue is tackled, we should add failure contract test cases for all the table tests in ibc_middleware_test.go (a couple tests can be modified to use the new failure contract, while others will need to have the test case added)