Pushing to ECR without logging in first doesn't work

[espadolini]

ko 0.15.2 fails to push images to ECR from GitHub actions without first running aws-actions/amazon-ecr-login.

The "Push to registries/Push to ECR" action in this very repo stopped passing since c23121a (https://github.com/ko-build/ko/actions/runs/7109904995/job/19355555999#step:6:18), so that's the likely culprit.

[cpanato]

That failure is because of some IAM changes in the account that removed the access to push, most likely. I cannot confirm 100% because I don't have access. But the test has been failing for a long time now

[espadolini]

I've had it fail just like that on a private repo, and work with no changes to the aws side after reverting from ko 0.15.2 to ko 0.15.1 or by adding an aws-actions/amazon-ecr-login step before the ko one.

[cpanato]

Hmm I see I will take a look

Thanks!