[.NET Migration Guide Revamp] [Phase 1] Move page 'Choose between .NET 5 and .NET Framework for server apps'

[StephenBonikowsky]

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

• Choose between .NET 5 and .NET Framework for server apps (MOVE) Move this page and its content to the new TOC location...

• name: Migration guide
  items:

  • name: Overview
    href: ../core/porting/index.md
  • name: General Information
    items:
    • name: Overview
      href: ../core/porting/general-information-overview.md
    • name: About .NET
      href: ../standard/choosing-core-framework-server.md

[StephenBonikowsky]

Completed with #24630