Make DIND image configurable and remove non-runner-containers helper to avoid unintended DIND inclusion

[matthew-collins-dailypay]

This PR updates the gha-runner-scale-set Helm chart templates to allow the DIND image to be configurable based on .Values.template.spec.containers. With this change, the chart will continue to use docker:dind by default, but if a container named dind is defined, that image is used instead. This provides greater flexibility for users who need to customize their DIND image.

As a result of making the DIND image configurable, the non-runner-containers helper now inadvertently includes the DIND container in scenarios where it’s not intended, specifically when using Kubernetes mode. To address this, we remove the non-runner-containers helper and rely exclusively on non-runner-non-dind-containers. This ensures that DIND remains properly scoped and does not appear where it should not.

[norman-zon]

also covered here: #3645. no reaction from the maintainers for months...

[FearlessHyena]

@Link- @nikola-jokic @rentziass
Would really like this and #3645 to be merged so #3709 can be supported
This seems to be a very straightforward change so could someone from GH please review and merge this?

[MKarytka-gastro]

Any update here, please? Important one.

[djetelina]

Hi, this would be really useful :)

[kohbis]

What's blocking the merge?
This change is convenient for users.

[cyrilico]

+1 for this, it's annoying to have to override a full spec when we just need to point to an internal registry

[nikola-jokic]

Please refer to this comment: #4219 (comment)

I will close this PR since it would require a redesign of the chart instead of a temporary fix. I understand that customizing just one field would result in larger values.yaml file, but I would disagree that it is highly inconvenient.