[typescript-axios] Handle sets as arrays in input parameters

[rgroothuijsen]

When an array is defined as having unique items, the generated Typescript model makes it a set instead of an array. However, this is an iterator instead of a concrete object. When passed to a JSON serializer, it results in the set being serialized as an empty object.

This PR changes the Axios templates to add a replacer function to JSON.stringify calls which turns any set into an array before serialization. Iterating over query parameters has also been changed to do so recursively if a parameter is either an array or a set.

Fixes #21663

@TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny @topce @akehir @petejohansonxo @amakhrov @davidgamero @mkusaka @joscha

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Summary by cubic

Ensure Sets generated for uniqueItems are serialized as arrays across the TypeScript Axios client to prevent empty-object payloads and broken headers/query params. Fixes #21663.

• Bug Fixes
  • Added replaceWithSerializableTypeIfNeeded and used it as a JSON.stringify replacer to serialize Set as Array.
  • Treated Set like Array in setFlattenedQueryParams for recursive query param handling.
  • Applied replacer in form-data Blobs and header serialization paths.
  • Updated imports/templates and regenerated samples.

^{Written for commit 5256bcb. Summary will update on new commits.}

[cubic-dev-ai]

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