[Reranko05]

Rationale for this change

This PR completes the repository-wide cleanup associated with the RapidJSON-to-simdjson migration

What changes are included in this PR?

• Remove obsolete RapidJSON references from build configurations, dependency manifests, CI images, and package definitions.
• Remove RapidJSON-specific CMake and Meson dependency configuration and obsolete support files.
• Clean up documentation and licensing references associated with the removed dependency.
• Exclude example code being handled in a separate PR (GH-51395: [C++][Docs] Replace RapidJSON with simdjson in row converter example #51396)

Are these changes tested?

CI will test.

Are there any user-facing changes?

No

Was AI used for this PR?

In accordance to the AI generation guidelines, please disclose below whether and how AI was used in this PR.

PR code and description written by:

• Human
• AI

Reviewed before submission by:

• Human
• AI
• Not reviewed

• GitHub Issue: [C++][Cleanup] Remove remaining RapidJSON references #55265

[github-actions]

⚠️ GitHub issue #55265 has no components, please add labels for components.