Show that a TestRun failed if the test fails - In ArgoCD and in TestRun conditions

### Feature Description

Usecase is that I want to deploy a new version of an API, then run x TestRuns on this api to verify it's still working.

The current [conditions](https://github.com/grafana/k6-operator/blob/14179cb9052fa0cead148d40e1f6cbaf421a2837/pkg/types/conditions.go) does not differenciate between a successful TestRun or a failing TestRun (in the example image below, thresholds of the k6 test is reached, the exit code is 99)

If we had a condition like this, we could make ArgoCD make these TestRun CRDs unhealthy with a "resource customization", preferably ready-to-use by everyone in [the ArgoCD repo](https://github.com/argoproj/argo-cd/tree/master/resource_customizations)

Image for reference:

### Suggested Solution (optional)

_No response_

### Already existing or connected issues / PRs (optional)

_No response_

Start with pkg/types/conditions.go and inspect how TestRun conditions represent success or failure. Then review the ArgoCD resource_customizations repository; done means a failed k6 threshold produces a distinct unhealthy TestRun condition that ArgoCD can recognize.

Written by the indexing model from the issue text.