Support setting custom collector image repo without custom tag

[Aransh]

Component(s)

collector

Is your feature request related to a problem? Please describe.

Opened following the discussion with @TylerHelmuth on open-telemetry/opentelemetry-helm-charts#1972

Currently when deploying the opentelemetry operator using the open telemetry-kube-stack, requires setting collector.image.tag alongside collector.image.repository in order to use a custom image on a collector.

For a use-case of using a custom image repo but the same tag, which follows the same versions (for example using "otel/opentelemetry-collector-contrib", or maybe a mirror), a user may want to set the image repo but still allow the chart maintainers to set the image tag that the operator is intended for (the one that will be used were there not a custom image repo set).

Describe the solution you'd like

See @TylerHelmuth's comment on open-telemetry/opentelemetry-helm-charts#1972 (comment)

Describe alternatives you've considered

I've considered doing this purely chart-side and set the . appVersion value as the custom tag if none is provided, but as Tyler mentioned in the discussion this is not viable

Additional context

No response

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