.Net: Processes - Tests for OnFunctionError events.

[alliscode]

Description

This PR adds one new integration test for processes where a step throws and exception and we expect the framework to emit an OnFunctionError event.

There are other minor changes to improve the de/serialization of events within the shared test infrastructure.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[esttenorio]