fix: oas31 response rendering

[pplr]

Handle rendering of response for OAS 3.1

Description

• No example displayed when the response has no content
• No exception when the response has no content or the content has no schema and defaultModelRendering is set to "model"

Motivation and Context

Fixes #9199

How Has This Been Tested?

Added an E2E test with a contract containing edge case responses:

• without content
• with content containing an empty media object
• with content containing a media object without schema but an example

Screenshots (if appropriate):

Before

After

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.

[glowcloud]

Thanks for the changes!

I included them in #9636 where I addressed the cause of getting "string" as an example, despite no example being defined. Your contribution will be properly attributed.