feat(tests): enhance sideContainers to support multi-containers tests

[alimx07]

Description

Enhance a SideContainers feature to the e2e test framework, with current spec (Name, Image, Cli, Volumes, NetMode) that can run alongside the primary unikernel, either joining its same named network or sharing its network namespace directly according to mode.

const (
	// sideContainerNetModeNetwork joins the same named/user-defined
	// network as the primary container (docker/nerdctl --network <name>).
	sideContainerNetModeNetwork sideContainerNetMode = "network"
	// sideContainerNetModeShared joins the primary container's network
	// namespace directly, similar to containers sharing a namespace
	// inside a Kubernetes pod (docker/nerdctl --network container:<id>).
	sideContainerNetModeShared sideContainerNetMode = "shared"
) 

Related issues

• Fixes Enhance SideContainers to Support Multi-Container Test Scenarios #845

How was this tested?

Still do not tested yet. I think the most easiet test will be a network calls on the localhost, so this is blocked until #793 merged.

LLM usage

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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