Make running forks a bit easier

[jukie]

This is to make it easier to run a fork with limited changes to the github actions.

• Splits up jobs so if a user doesn't have ECR configured for example the others can still execute
• Allows for setting OVERRIDE_ image tags at the repo level so a fork user can push to their own registries.

For context I'm changing the output format in the fluent plugin like this but would still like to have an easy process for syncing the fork without dealing with conflicts every time.

[swiatekm]

Would it also help to make the jobs conditional on the required secrets existing?

I'm ok with this change overall, but I don't like duplicating the tag extraction logic in each job. Could we move that to a separate job that the rest can depend on?