docker: fix a bug where auth for private registries wasn't parsed correctly

[pkazmierczak]

In #23966 we introduced an official Docker client and did not notice that in contrast to our previous 3rd party client, the official SDK PullOptions object expects a base64 encoded JSON with username and password, instead of username/password pair.

This PR fixes the issue and adds e2e tests for Docker driver auth.

Fixes #24181
Internal ref: https://hashicorp.atlassian.net/browse/NET-11310

[tgross]

👻

[pkazmierczak]

One other thing: the e2e tests are failing because the local registry isn't added to dockerd's "insecure registries." I'm not sure how to add it since we only know the registry address once we create it, I'll have to think about it.

[shoenig]

The podman e2e test jumps through some fun hoops to setup a private registry that is auth enabled, can take a look for inspiration maybe. https://github.com/hashicorp/nomad/blob/main/e2e/podman/input/registry-auths.hcl

[gjrtimmer]

I had to rollback to 1.8.4, this issues caused several hours of downtime. When is this going to be fixed?

[tgross]

@gjrtimmer it should be obvious that this is actively being worked on. Updates on when this will be shipped will be posted to the original issue when available. If you skipped pre-production testing, please reach out to your Enterprise support contact if any to get help in rolling back if you need it.

[tgross]

LGTM, nice work on this