refactor: decouple schema naming from discriminator mapping introspection

[Mattias-Sehlstedt]

Decouples the toModelName (e.g., adding a prefix or a suffix) Codegen functionality from the getAllOfDescendants and getOneOfAnyOfDescendants discriminator introspection methods. This is in preparation for these methods being moved to the DiscriminatorUtils class.

This is done so that the discriminator logic can later be clarified and optimized, since as of current there are several passes over the entire specification when searching for the discriminator mappings. A single walk along the path for each discriminator schema should be enough to gather all the necessary information for building the typing and the mapping for the discrimination.

There is also the rather crude implementation of the specification analysis, where it should be preferable to utilize the visitedSchemas approach (walk the path recursively and keep a log of what schemas that have been visited to terminate loops).

This PR also breaks out the building of a larger error message when failing to interpret a discriminator, and it also creates a helper for repeated vendor extension introspection.

PR checklist

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  ./bin/utils/export_docs_generators.sh || exit
  

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Summary by cubic

Decouples schema naming from discriminator mapping introspection so mappings use raw schema names, with toModelName applied once during discriminator creation. Centralizes x-discriminator-value lookup and discriminator error building in DiscriminatorUtils; no behavior change expected.

• Refactors
  • getAllOfDescendants and getOneOfAnyOfDescendants now return schema-name-based MappedModel; new adjustModelNames() in DefaultCodegen applies toModelName during createDiscriminator.
  • Added DiscriminatorUtils.discriminatorVendorExtensionValue(...) and DiscriminatorUtils.getDiscriminatorSchemaError(...); replaced inline vendor extension access and error message assembly.

^{Written for commit a4d71b3. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 2 files

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