This adds the ability do use complex objects that are passed through to
the assertoor config in json format.
It allows defining assertoor tests like this via the kurtosis params:
```
assertoor_params:
  run_stability_check: false
  run_block_proposal_check: true
  tests:
    - file: https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/block-proposal-check.yaml
      timeout: 2h
      config:
        someCustomTestConfig: "some value"
```

The old way to specify the link to the test only is still supported:
```
assertoor_params:
  run_stability_check: false
  run_block_proposal_check: true
  tests:
    - "https://raw.githubusercontent.com/ethpandaops/assertoor-test/master/assertoor-tests/block-proposal-check.yaml"
```

Effectively both formats can be used.


The downstream implementation is unfortunately not super nice 😅
It embeds the test configs as json objects within the yaml
configuration.
This works fine as yaml inherits the json syntax.