fix: garden publish deploymentImageId for container actions

[Walther]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #4796

Special notes for your reviewer:

WIP attempt, do not merge yet

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EDIT: not the right fix, I was mistakenly looking at the wrong place: this would only affect the container provider (TIL!), which we rarely use (e.g. here for circleci-runner etc). (Sidenote: the container provider is probably currently also unable to publish anywhere other than dockerhub? Unsure if it warrants more investigation / possible fix.)

The actual issue is in the publish method of the kubernetes provider as before, core/src/plugins/kubernetes/container/publish.ts, or in the implementation of action.getOutput("deploymentImageId").

Notably, after #4740 we do take into account the deploymentRegistry, but if you are only using the publishId field, it does not appear to get used the right way.