feat: scriptless mode in NBC so we can move in phases

[awesomenix]

What this PR does / why we need it:

Switch to using scriptless but with CSE for Phase 1

Which issue(s) this PR fixes:

Fixes #

[Copilot]

Pull request overview

This PR implements Phase 1 of transitioning to scriptless node bootstrapping by moving LocalDNS configuration from CustomData to CSE environment variables, while maintaining backward compatibility during the migration period.

Changes:

• LocalDNS configuration moved from cloud-init CustomData to CSE environment variables (SHOULD_ENABLE_LOCALDNS, LOCALDNS_CPU_LIMIT, LOCALDNS_MEMORY_LIMIT, LOCALDNS_GENERATED_COREFILE)
• Refactored LocalDNS enablement logic to support both legacy (corefile in VHD) and new (corefile generated at provision time) deployment modes
• Modified GenerateLocalDNSCoreFile to return empty string instead of error when LocalDNS is disabled, allowing graceful handling
• E2E tests updated to use minimal customData placeholder while CSE variables carry the configuration

Reviewed changes

Copilot reviewed 35 out of 133 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pkg/agent/testdata/*/CSECommand	Snapshot tests regenerated with new SHOULD_ENABLE_LOCALDNS, LOCALDNS_CPU_LIMIT, LOCALDNS_MEMORY_LIMIT, LOCALDNS_GENERATED_COREFILE environment variables
pkg/agent/baker_test.go	Removed tests expecting errors when LocalDNSProfile is nil or disabled (now returns empty string)
pkg/agent/baker.go	Changed GenerateLocalDNSCoreFile to return ("", nil) instead of errors when LocalDNS disabled
parts/linux/cloud-init/artifacts/cse_main.sh	Simplified LocalDNS enablement to single conditional path
parts/linux/cloud-init/artifacts/cse_config.sh	Refactored enableLocalDNS functions: extracted generateLocalDNSFiles, unified enableLocalDNS logic to handle both legacy and new modes
parts/linux/cloud-init/artifacts/cse_cmd.sh	Added 4 new LocalDNS-related environment variables to CSE command
e2e/vmss.go	Changed customData to minimal placeholder (base64 "#cloud-config\n") for scriptless testing

[Copilot]

Pull request overview

Copilot reviewed 35 out of 133 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 40 out of 138 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (2)

pkg/agent/baker.go:1867

• The comment above the return is now inaccurate: GenerateLocalDNSCoreFile returns the plain Corefile string (not gzipped+base64). Either update the comment to reflect the new contract or move the encoding responsibility documentation to the template funcs (GetGeneratedLocalDNSCoreFile / GetCSEGeneratedLocalDNSCoreFile).

# WARNING: Changes to this file will be overwritten and not persisted.
# ***********************************************************************************

parts/linux/cloud-init/artifacts/cse_config.sh:1196

• enableLocalDNS exits the whole script on failure (systemctlEnableAndStart ... || exit $ERR_LOCALDNS_FAIL). Since it’s wrapped in logs_to_events, exiting inside the function can bypass the wrapper’s error logging/cleanup. Prefer returning a non-zero status and let the caller handle exiting.

    echo "localdns should be enabled."
    systemctlEnableAndStart localdns 30 || exit $ERR_LOCALDNS_FAIL
    echo "Enable localdns succeeded."

[Copilot]

Spelling: "Any overriden files" should be "Any overridden files".

Suggested change

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	Any overridden files will be listed here - Hotfix mode