Fix configs to allow the use of configs as keys of other configs

[romain-intel]

This allows things like this:

def git_info(args):
    info = {
        "commit": ["git", "rev-parse", "HEAD"],
        "branch": ["git", "rev-parse", "--abbrev-ref", "HEAD"],
        "message": ["git", "log", "-1", "--pretty=%B"],
    }
    cfg = {}
    for key, cmd in info.items():
        cfg[key] = check_output(cmd, text=True).strip()
    if cfg["branch"].startswith("feature/"):
        cfg["branch_type"] = "feature"
    elif cfg["branch"].startswith("main"):
        cfg["branch_type"] = "main"
    else:
        cfg["branch_type"] = "default"]
    print(f"cfg is {cfg}")
    return cfg

class MyExampleCICDFlow(FlowSpec):
    git_config = Config("git_config", default_value={}, parser=git_info)
    flow_config = Config("flow_config", default="my_config.json")

    @timeout(seconds=flow_config[git_config.branch_type].timeout)
    @step
    def start(self):
        # More code