fix(server): fix issues when running tests

[schoren]

This PR fixes some issues when running tests.

1. The test run cache was causing issues, and is no longer required, so it's removed.
2. When mapping trigger results from openapi to internal models, an empty GRPC result was becoming an empty object instead of nil in the internal model, creating some confusion when handling results later
3. The query to get the test suite run steps was using an incorrect sort field, causing the list to be in an unexpected order.

Changes

Fixes

Checklist

• tested locally
• added new dependencies
• updated the docs
• added a test

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