This adds an e2e regression test for authenticated pull/push against a private registry, covering the auth regression reported in docker/cli#5963.
Includes:
- New privateregistry service in the e2e Compose stack with htpasswd auth on port 5001, and --insecure-registry for the engine container.
- TestPullPushPrivateRepository test that verifies authenticated push/pull and rejects unauthenticated operations.
- Auth config and test credentials in e2e/testdata/registry/.
- 90-second retry loop for transient DNS/container startup races.
- Service health wait loop in scripts/test/e2e/run.
- Increase TestProcessTermination timeout from 10s to 20s for connhelper-ssh + engine 25 combination.
- Connhelper-ssh engine Dockerfile for private registry integration.
Signed-off-by: Lohit Kolluri <lohitkolluri@gmail.com>
