Adapt get_environment for ToySGD to be consistent with other environments

[Bronzila]

Here you can see the difference:

if env_config["type"] == "ToySGD":
        # setup benchmark
        bench = ToySGD2DBenchmark()
        bench.config.cutoff = env_config["num_batches"]
        bench.config.low = env_config["low"]
        bench.config.high = env_config["high"]
        bench.config.function = env_config["function"]
        bench.config.initial_learning_rate = env_config["initial_learning_rate"]
        bench.config.state_version = env_config["state_version"]
        bench.config.reward_version = env_config["reward_version"]
        bench.config.boundary_termination = env_config["boundary_termination"]
        bench.config.seed = env_config["seed"]
        return bench.get_environment()
    if env_config["type"] == "SGD":
        bench = SGDBenchmark(config=env_config)

In order to adapt it, we would need to adjust our config file to feature all important information or add it throughout initialization (such as e.g., the seed). Currently it would suffice to simply add a default instance_set_path. However, if we change this we should double check that this does not affect reproducibility.