[typescript] Fix missing model imports for container types in oneOf schemas (#23286)

[cpruijsen]

The typescript and typescript-redux-query generators now keep model imports for container branches of oneOf schemas.
For the circular schema in #23286, typescript generated Array<Repro> | string without the necessary Repro import.

Both filters use CodegenProperty.getImports with parsed branch metadata.
The filters keep direct references, remove unused imports, and keep imports sorted.
The substring comparison from the issue can keep an unused Foo import for a FooBar branch.

Fixes #23286.

The regression test in modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/TypeScriptClientCodegenTest.java failed without the changes and passed with them.
The TypeScript package tests passed.

PR checklist

• Read the contribution guidelines.
• Run the complete project build, all sample generation, and generator documentation export.
• Mention the TypeScript technical committee members.

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

---

Summary by cubic

Fixes missing model imports for container types in oneOf schemas in the typescript and typescript-redux-query generators, resolving circular schema generation issues from #23286.

Previously, model imports were kept only when they matched a direct oneOf branch name, so a branch like Array<Repro> lost the Repro import. The filters now resolve imports from each branch's parsed metadata so inner types of container branches retain their imports, while unused imports are still removed and ordering is preserved.

Adds a regression test with a circular oneOf schema (Array<Repro> | string) covering both generators.

^{Written for commit ff4e1b4. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

_{View guided diff | Re-trigger cubic}