[Meta] Migrate Ruby API&SDK documentation to new structure

[svrnm]

Tasks

• Rename "Getting Started" to "Getting Started by Example"
• Replace Instrumentation, Libraries, Exporters, Sampling 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 Ruby" page
• Add any additional pages and resources that the Ruby 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 Ruby

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