Add UUID examples and documentation

[epou]

This PR updates the examples and documentation to use UUID fields of type UUID instead of str.

While str works for UUID fields (since Pydantic automatically casts strings to UUID objects), using the actual UUID type provides better clarity and type consistency in the generated models and examples.
Notes:

• This change introduces UUID to languageSpecificPrimitives, similar to how datetime is handled.
• The uuid package is part of Python’s standard library, so this doesn’t add any external dependencies.
• Although using str isn’t technically incorrect, adopting UUID makes the documentation more explicit and aligned with real-world usage.

Relates to PR #21740

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• If your PR solves a reported issue, reference it using GitHub's linking syntax (e.g., having "fixes #123" present in the PR description)
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