test(e2e): add podman rust suite

[drew]

Summary

Add a Podman-backed Rust e2e entrypoint and make the Rust e2e crate select driver-specific suites with Cargo features instead of runtime skips.

Related Issue

N/A

Changes

• Add e2e/with-podman-gateway.sh and shared gateway wrapper helpers used by Docker and Podman e2e runs.
• Make L7 proxy Rust e2e tests use a driver-neutral container helper and GHCR-hosted test server image.
• Split Rust e2e tests into e2e, e2e-docker, and e2e-docker-gpu Cargo suites.
• Update Podman driver host aliases and namespace labeling for e2e cleanup and host reachability.
• Collapse mise run e2e:podman to a single Rust e2e task.

Testing

• mise run pre-commit passes
• cargo test --manifest-path e2e/rust/Cargo.toml --features e2e --no-run
• cargo test --manifest-path e2e/rust/Cargo.toml --features e2e-docker --no-run
• cargo test --manifest-path e2e/rust/Cargo.toml --features e2e-docker-gpu --no-run
• Live mise run e2e:podman not run in this session

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable)

[github-actions]

Label test:e2e applied for de6b8d9. Open the existing run and click Re-run all jobs to execute with the label set. The E2E Gate check on this PR will flip green automatically once the run finishes.

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[drew]

/ok to test 33cb82a

[drew]

/ok to test 7b7a8c6

[drew]

/ok to test f2bd488

[drew]

/ok to test e67bd05

[drew]

/ok to test fd5e1af

[github-actions]

🌿 Preview your docs: https://nvidia-preview-pr-1185.docs.buildwithfern.com/openshell

[elezar]

Two minor cleanup / simplification comments, but looks good in general.

[drew]

/ok to test b3ed5d9

[drew]

/ok to test 81fa1ed