New-CI: Implement Build Installers Stage

[andrew-m-leonard]

Title: Create installer building stage

Description:
Implement the Build Installers stage that creates platform-specific installers (MSI, PKG, DEB, RPM).

Tasks:

• Create 07-installer.sh script (already exists, may need updates)
  • Read signed JDK from INPUT_ARTIFACTS_DIR
  • Build platform-specific installers
  • Write installers to TARGET_DIR
  • Generate installer metadata
• Add stage to Jenkinsfile.declarative
  • Define stage with proper prerequisites
  • Set INPUT_ARTIFACTS_DIR and TARGET_DIR
  • Add artifact archiving
• Add stage to run-pipeline.py
  • Implement stage_installer() method
  • Set environment variables
  • Handle workspace cleanup
• Test stage locally
• Test stage in Jenkins
• Document stage behavior

Acceptance Criteria:

• Script works in both Jenkins and local
• Installers created correctly
• All installer types supported
• Stage is restartable
• Documentation complete