[release/10.0] OpenAPI: Fix Circular reference in specific order gives empty schema

[github-actions]

Backport of #63511 to release/10.0
/cc @captainsafia @desjoerd

OpenAPI: Fix Circular reference in specific order gives empty schema

Summary of the changes (Less than 80 chars)
Fix circular reference resolution to prevent empty schemas regardless of property order

Description

This PR fixes an issue in the OpenAPI schema generation service where circular references could result in empty schemas for referenced types depending on the order of property declarations. The fix changes the schema reference resolution logic from using AddOpenApiSchemaByReference to directly creating OpenApiSchemaReference objects

Fixes #63503

Customer Impact

Customers using ASP.NET Core's OpenAPI generation with models containing circular references may experience incomplete or empty schemas in their OpenAPI documents, particularly when the order of properties affects schema processing. We can consider this a follow-on the the circular reference fixes that we included in .NET 10 Preview 7.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

This is a targeted fix that only changes the reference creation mechanism without affecting the broader schema generation architecture. The change is minimal and there's existing and new test coverage in the space.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A