Adding k6-browser support to runner image

[javaducky]

Add support for distributed k6-browser scripts.

[javaducky]

@yorugac, building upon our Slack convo today, I successfully ran k6-browser tests using the operator. There remains a separate issue where only parallelism: 1 being supported due to parsing of browser-specific options causing maxVUs=1.

This PR is more of an FYI (experiment)...I'm not sure if we truly want to merge this just yet.

[yorugac]

Related PR for Docker k6-browser image: grafana/k6#3340

@javaducky, IIUC, the browser image worked for you even without this no-sandbox option? I've got an impression that it wasn't supposed to work without it 😅 Well, now it's hard-coded anyway, but it's a curious situation.

I've checked the case of maxVUs > 1: it seems parallelism is working correctly with browser as well 👍

I think from k6-operator perspective, just knowing of this second image with browser support is sufficient: it's too large to make a default runner image. IOW, it'd be good if we could make a remark on browser images in the docs, at some point.

[javaducky]

the browser image worked for you even without this no-sandbox option?

Yes. I didn't seem to have any issues related to this. 🤷

I've checked the case of maxVUs > 1: it seems parallelism is working correctly with browser as well 👍

Here is my scenario. I'm using a test script using the constant-vus executor specifying vus: 4.

My K6 resource successfully executes if parallelism: 1, but fails if I try to use parallelism: 2 with the following output in the manager log (log line truncations due to display in k9s):

│ 2023-09-20T13:51:20Z    INFO    controllers.K6    Waiting for initializing pod to finish    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "6 │
│ 2023-09-20T13:51:20Z    INFO    controllers.K6    Reconcile(); stage = initialization    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "50f6 │
│ 2023-09-20T13:51:20Z    INFO    controllers.K6    k6 inspect: {External:{Loadimpact:{Name: ProjectID:0}} TotalDuration:10s MaxVUs:1 Thresholds:map[checks:0xc000a │
│ 2023-09-20T13:51:20Z    ERROR    controllers.K6    Parallelism argument cannot be larger than maximum VUs in the script    {"namespace": "k6-demo", "name": "k6-b │
│ github.com/grafana/k6-operator/controllers.RunValidations                                                                                                         │
│     /workspace/controllers/k6_initialize.go:69                                                                                                                    │
│ github.com/grafana/k6-operator/controllers.(*K6Reconciler).Reconcile                                                                                              │
│     /workspace/controllers/k6_controller.go:121                                                                                                                   │
│ sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Reconcile                                                                                    │
│     /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.14.6/pkg/internal/controller/controller.go:122                                                                  │
│ sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).reconcileHandler                                                                             │
│     /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.14.6/pkg/internal/controller/controller.go:323                                                                  │
│ sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).processNextWorkItem                                                                          │
│     /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.14.6/pkg/internal/controller/controller.go:274                                                                  │
│ sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller).Start.func2.2                                                                                │
│     /go/pkg/mod/sigs.k8s.io/controller-runtime@v0.14.6/pkg/internal/controller/controller.go:235                                                                  │
│ 2023-09-20T13:51:20Z    INFO    controllers.K6    Reconcile(); stage = error    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "87bb5821-7853 │
│ 2023-09-20T13:51:21Z    INFO    controllers.K6    Reconcile(); stage = error    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "2a325800-3f65 │
│ 2023-09-20T13:51:21Z    INFO    controllers.K6    Reconcile(); stage = error    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "c3215c34-0448 │
│ 2023-09-20T13:51:21Z    INFO    controllers.K6    Reconcile(); stage = error    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "fd1fe89c-37cc │
│ 2023-09-20T13:51:21Z    INFO    controllers.K6    Reconcile(); stage = error    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "904cca7e-40c0 │
│ 2023-09-20T13:51:25Z    INFO    controllers.K6    Reconcile(); stage = error    {"namespace": "k6-demo", "name": "k6-browser-test", "reconcileID": "bc4f700e-571f │