[#54296] PDF export gantt chart

[as-op]

Use prawn to export Gantt chart in background worker

• [x] Subject of work package in first column
• [x] "Zoom"
  • [x] Day, month or quarter based view
  • [x] Adjustable column sizes
• [x] Split chart on pages depending on PDF "paper" size
• [x] Vector based shapes in PDF
• [x] Work package type defines bar color
• [x] Work package type "milestone" is a diamond shape
• [x] Chart header repeats on every page
• [x] work package sorting
• [x] Dependency lines between work packages (follows-precedes relationships)
• [x] work package hierarchies with index numbers
• [x] work package groupings
• [x] Refactor humongous app/models/work_package/pdf_export/gantt.rb
• [x] Remove DEBUG UI from Export modal
• [x] Add UI Options described in https://community.openproject.org/projects/openproject/work_packages/54297

https://community.openproject.org/work_packages/54296