testutils: Convert the workflow spec to and from proto in ensureGraph

[ferglor]

In this PR, we're modifying the ensureGraph function within testutils' Runner to convert the workflow spec to a protobuf, and then back again, to get around an issue I encountered while developing a workflow

Specifically, I was using the read contract capability in my workflow, but when I ran my unit test against the workflow, I got this error:

invalid refs map[ConfidenceLevel:finalized Params:map[fundTokenId:0xd4b2f7c3e5f28c8d0a34b17b9ce5d6d7e85a9bcf1e6a7d8e3c2a5f9b8d4e6c3d]] for step read

I was using the capability like so:

chainRead := readcontract.Config{
			ContractAddress:      config.DataSourceContractAddress,
			ContractName:         config.DataSourceContractName,
			ContractReaderConfig: config.DataSourceContractConfig,
			ReadIdentifier:       fmt.Sprintf("%s-%s-%s", config.DataSourceContractAddress, config.DataSourceContractName, config.DataSourceContractFunction),
		}.New(
			w,
			"[email protected]",
			"read",
			readcontract.ActionInput{
				ConfidenceLevel: sdk.ConstantDefinition("finalized"),
				Params: sdk.ConstantDefinition(readcontract.InputParams{
					"fundTokenId": config.DataSourceFundTokenID,
					"_unused":     cron.Ref(), // TODO: Figure out a nicer way to do this.
				}),
			})

And mocking it like this:

contractRead := readcontractcaptest.Action(runner, "[email protected]", func(input readcontractcap.Input) (readcontractcap.Output, error) {
		b, err := json.Marshal(map[string]any{
			"nav":         "123",
			"fundTokenId": "0xd4b2f7c3e5f28c8d0a34b17b9ce5d6d7e85a9bcf1e6a7d8e3c2a5f9b8d4e6c3d",
		})

		if err != nil {
			return readcontractcap.Output{}, err
		}

		return readcontractcap.Output{
			LatestValue: b,
		}, nil
	})

It seems the issue I encountered is specific to local unit testing only; that is, if I was testing my code remotely I would not have encountered this.

Therefore, we're adding serializing and deserializing steps to the local test runner to bypass this issue

[justinkaseman]

Change makes sense. Thanks for dealing with this.