[release/9.0] Fix handling for inert route parameters in MVC endpoints for OpenAPI

[github-actions]

Description

Backport of #58246 to release/9.0.

This PR makes the OpenAPI implementation more resilient to "inert route parameters" in MVC. Inert route parameters appear in the route template but are never bound to in the route handler. For example:

[Route("/api/{version}/{id})]
public void GetItem(int id) { } // `id` doesn't appear here

This pattern happens frequently when users integrate with the API versioning package which uses inert route parameters to distinguish between different versions of an API.

Fixes #58219

Customer Impact

Without this PR, customers are not able to generate OpenAPI specs for APIs that are versioning with the API versioning package and use version numbers in the URL.

There are no workarounds for this issue.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Change is localized to OpenAPI package and makes the package more resilient to bad inputs.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

[captainsafia]

Approved via email.