fix: add default CSE_TIMEOUT directly within cse_start.sh

[cameronmeissner]

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

[Copilot]

Pull request overview

Updates Linux CSE startup logic to apply a default global execution timeout when CSE_TIMEOUT is unset/empty, and refreshes generated CustomData test snapshots to match the new rendered script content.

Changes:

• Use ${CSE_TIMEOUT:-15m} in cse_start.sh so CSE has a default 15-minute global timeout.
• Regenerate multiple pkg/agent/testdata/**/CustomData* snapshot artifacts to reflect the updated CSE script output.

Reviewed changes

Copilot reviewed 60 out of 63 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
parts/linux/cloud-init/artifacts/cse_start.sh	Adds default timeout value for CSE execution when CSE_TIMEOUT is unset/empty.
pkg/agent/testdata/MarinerV2+Kata/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/MarinerV2+CustomCloud/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/MarinerV2+CustomCloud+USSec/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/MarinerV2+CustomCloud+USNat/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/Flatcar/CustomData.inner	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/Flatcar+CustomCloud/CustomData.inner	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/Flatcar+CustomCloud+USSec/CustomData.inner	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AzureLinuxV3+Kata/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AzureLinuxV2+Kata/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2404+Teleport/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2404+NetworkPolicy/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+ootcredentialprovider/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+cgroupv2/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+SerializeImagePulls/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+SecurityProfile/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+SSHStatusOn/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+SSHStatusOff/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+OutboundTypeNone/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+OutboundTypeNil/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+OutboundTypeBlocked/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+NoArtifactStreaming/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+MigStrategy+Single/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+MigStrategy+None/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+MigStrategy+Mixed/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+IMDSRestrictionOff/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+EnableManagedGPU/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+CustomCloud/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.
pkg/agent/testdata/AKSUbuntu2204+China/CustomData	Regenerated CustomData snapshot to match updated CSE start script behavior.