[.NET Migration Guide Revamp] [Phase 1] Move content of page 'Organize projects for .NET'

[StephenBonikowsky]

For details on revamp see: #23561
New TOC: #23215

• Organize projects for .NET (MOVE) Move this page to the new TOC location...

• name: Migration guide
  items:

  • name: Overview
    href: ../core/porting/index.md
  • name: General Information
    items:
  • name: Pre-Migration
    items:
  • name: Migration
    items:
    • name: Create a porting plan
      items:
      • name: Overview
        href: ../core/porting/create-a-porting-plan.md
      • name: Project structure
        href: ../core/porting/project-structure.md

[StephenBonikowsky]

Completed with #24630