Add support for the new `beforeStep` and `afterStep` fixtures

[Robert-96]

Modify the .NET executor to accept an extra argument containing the step details (e.g., step id, name, model name) introduced by the beforeStep and afterStep fixtures.

This change will enable users to access step-specific information within beforeStep and afterStep fixtures when using the .NET executor.

See altwalker/altwalker#33 for more details.