tests/integration: Run flux check after installation

[darkowlzz]

Run flux check after installation to show the relevant cluster and resource configurations in the environment.

...
2024/05/10 14:43:02 Installing flux
2024/05/10 14:43:50 Running flux check
► checking prerequisites
✔ Kubernetes 1.28.7-gke.1026000 >=1.26.0-0
► checking version in cluster
✔ distribution: flux-v0.0.0-dev.0
✔ bootstrapped: true
► checking controllers
✔ helm-controller: deployment ready
► ghcr.io/fluxcd/helm-controller:v1.0.0
✔ image-automation-controller: deployment ready
► ghcr.io/fluxcd/image-automation-controller:v0.38.0
✔ image-reflector-controller: deployment ready
► ghcr.io/fluxcd/image-reflector-controller:v0.32.0
✔ kustomize-controller: deployment ready
► ghcr.io/fluxcd/kustomize-controller:v1.3.0
✔ notification-controller: deployment ready
► ghcr.io/fluxcd/notification-controller:v1.3.0
✔ source-controller: deployment ready
► ghcr.io/fluxcd/source-controller:v1.3.0
► checking crds
✔ alerts.notification.toolkit.fluxcd.io/v1beta3
✔ buckets.source.toolkit.fluxcd.io/v1beta2
✔ gitrepositories.source.toolkit.fluxcd.io/v1
✔ helmcharts.source.toolkit.fluxcd.io/v1
✔ helmreleases.helm.toolkit.fluxcd.io/v2
✔ helmrepositories.source.toolkit.fluxcd.io/v1
✔ imagepolicies.image.toolkit.fluxcd.io/v1beta2
✔ imagerepositories.image.toolkit.fluxcd.io/v1beta2
✔ imageupdateautomations.image.toolkit.fluxcd.io/v1beta2
✔ kustomizations.kustomize.toolkit.fluxcd.io/v1
✔ ocirepositories.source.toolkit.fluxcd.io/v1beta2
✔ providers.notification.toolkit.fluxcd.io/v1beta3
✔ receivers.notification.toolkit.fluxcd.io/v1
✔ all checks passed
2024/05/10 14:43:59 Running e2e tests
=== RUN   TestFluxInstallation
...

Example run: https://github.com/fluxcd/flux2/actions/runs/9034019891/job/24825614710?pr=4778#step:13:109

[stefanprodan]

LGTM

Thanks @darkowlzz 🏅