feat: prototype demonstrating proposed swappable graph yaml

[keithmanville]

No description provided.

[keithmanville]

As discussed, we will stick with the following format for specifying swaps:

load_model:
  model:
    name: $name
attack_step:
  ?attack:
    attack1:
      model: $model
      epsilon: $eps
    attack2:
      model: $model
      epsilon: $eps
      iterations: $n

We will not implement any provisions for supporting anchors/aliasing.

Leaving this draft PR open for reference. The prototype may be helpful in implementing other issues.