test(e2e): pull container images on-demand for filtered test runs

[Nachiket-Roy]

Description

The end-to-end test suite previously pulled all declared container images in BeforeAll regardless of test filters. When executing a filtered subset of tests (such as make test_nerdctl_Spt or specific CI/CD jobs), this incurred unnecessary network overhead, bandwidth usage, and pull flakiness.
The test framework now:

• Pulls images on-demand: Images and sidecars are pulled only when a matching spec executes (before pod or container creation).
• Prevents duplicate pulls: Uses a simple thread-safe in-memory map to ensure each image is pulled at most once per test run.
• Cleans up pulled images: DeferCleanup only removes images that were actually downloaded during the test run.
• Reuses existing abstractions: Leverages tool.Name() ("ctr", "crictl", "docker", "nerdctl") without introducing extra types or interface methods.

Related issues

• Fixes PUll only the images to test #1037

How was this tested?

1. Build and Compilation

   go build ./... && go test -c ./tests/e2e -o /dev/null

   The entire codebase and e2e test harness compile cleanly without errors.

2. Full Unit Test Suite

   make unittest

   All unit tests across pkg/network, pkg/unikontainers, pkg/unikontainers/hypervisors, pkg/unikontainers/initrd, pkg/unikontainers/unikernels, and internal/metrics passed with zero errors.

3. Filtered Dry‑Run Verification

   go test ./tests/e2e -v -run TestE2E --ginkgo.focus="Nerdctl.*Spt" --ginkgo.dry-run

   Output:

   Will run 4 of 75 specs
   SSSSSSSSSSSSSSSSSSS•SSSSSSS•••SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS
   Ran 4 of 75 Specs in 0.002 seconds
   SUCCESS! -- 4 Passed | 0 Failed | 0 Pending | 71 Skipped
   

   Only the 4 matching specs were targeted, and no unneeded images from the remaining 71 test cases were queued or pulled.

LLM usage

Gemini 3.8

Checklist

• I have read the contribution guide.
• The linter passes locally (make lint).
• The e2e tests of at least one tool pass locally (make test_ctr, make test_nerdctl, make test_docker, make test_crictl).
• If LLMs were used: I have read the llm policy.

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[cmainas]

Hello @Nachiket-Roy ,

there are multiple issues with this proposal:

• The ToolType replicates the Name method.
• The issue did not mention to retain images
• I can not really understand the purpose of the lock
• There is no reason to check if an image exists, An existing image will not get pulled again.

This implementation is unnecessary overcomplicated.

[Nachiket-Roy]

Thanks for the review. I have resolved them and simplified the PR

• The ToolType replicates the Name method.

Reverted

• The issue did not mention to retain images

sure removed it

• I can not really understand the purpose of the lock

Added to be concurrent safe but that is already handled so droped

• There is no reason to check if an image exists, An existing image will not get pulled again.

Dropped

please take a look again.