[Meta] Migrate .NET API&SDK documentation to new structure

[svrnm]

Tasks

• Rename "Getting Started" to "Getting Started by Example"
• Replace Instrumentation, Libraries, Exporters, Resources pages with "Record Telemetry with the API", "Manage Telemetry with the SDK", "Configure the SDK" and "Configure the SDK" pages
• Add "Instrumentation ecosystem" page
• Add "Intro to OpenTelemetry .NET" page
• Review if "Tracing Shim" page is still needed or can be incorporated into any of the other new pages
• Add any additional pages and resources that the .NET SIG likes to add within their space

Background

Based on Restructure Language SDK & API documentation information architecture - #4853 we rolled out an updated information architecture for the language API & SDK documentations for Java via #4966 and other PRs: https://opentelemetry.io/docs/languages/java/api/

As announced on the discussion and during a maintainer's call we want to roll out the same changes across all other languages. This is the meta issue for .NET

cc @open-telemetry/dotnet-approvers -approvers @open-telemetry/dotnet-maintainers