Reduce transient DE legacy test job failures during dependency artifact download

[Copilot]

The failing Build Unit Tests (DE) (LegacyTestsBucket1) job was not failing in AL compilation or test execution; it was timing out while downloading dependency artifacts in the AL-Go pipeline. This change reduces that contention-driven failure mode by widening the startup staggering applied to test projects.

• Root cause

  • Download Project Dependencies failed with Failed to GetSignedArtifactURL: ETIMEDOUT
  • The job had already downloaded most artifacts successfully, pointing to transient saturation on parallel test-job startup rather than a DE-specific product defect

• Change

  • Widen the shared randomized startup delay used by test projects before AL-Go begins heavy dependency pulls
  • Increase the jitter window from 0–180s to 0–600s in the central test-project BuildInitialize hook

• Scope

  • Keep the change centralized in the shared hook used by build/projects/Test Apps */.AL-Go/BuildInitialize.ps1
  • Avoid per-country/per-project customization; DE benefits through the existing shared test-project path

• Guardrail

  • Add a focused Pester test covering the widened delay range so the hook behavior stays explicit and reviewable

$maxDelaySeconds = 600
$delaySeconds = Get-Random -Minimum 0 -Maximum ($maxDelaySeconds + 1)
Start-Sleep -Seconds $delaySeconds