repeating setup steps

**Is your feature request related to a problem? Please describe.**

Sometimes you need to call a setup step lots of times. The easy approach to this is to write a helper smart contract that loops your setup operations for you, so in contender, you can just call one function that does a lot of setup work. But if your target function uses too much gas, you're limited to some number of iterations before you run out of gas.

If we could just repeat setup steps and provide each step with a value from an iterator that provides new args (i.e. the index of the token to mint from the array of tokens you have), then this problem would be solved.

**Describe the solution you'd like**

Add a field to `[[setup]]` steps:

```toml
repeat = { param = "x", start_value = 0, increment ?= 1, decrement ?= 0, count = 5 }
```

that makes the step repeat `count` number of times, incrementing the argument to `param` (a function parameter name) by `increment`, or decrementing by `decrement`, with the value starting at `start_value`.