Spruce up `OpenApiResponse` creation in `Microsoft.AspNetCore.OpenApi` package

[captainsafia]

With the introduction of the Microsoft.AspNetCore.OpenApi package, we carried over some logic for producing OpenApiResponses out of the metadata and attributes that a handler had that existing in the ApiExplorer.

This logic assumes some MVC-specific patterns and is fairly complex to reason about, especially when it comes to processing content types that are set on an endpoint.

The new package gives us an opportunity to break away from this tradition and adopt a more simplified hierarchy for how Produces attributes and metadata are processed on an endpoint.

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We're moving this issue to the .NET 7 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
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[captainsafia]

Moving this to the backlog.

Changing up our response generation for minimal isn't going to add a ton of value and will likely introduce more bugs into this surface area.

We might even want to consider closing this all together unless we can design a radically simplified/approachable response generation strategy in the OpenAPI package.

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[captainsafia]

If we take the strategy outlined in #43675, we should see about removing the inference logic in the generator and relying on setting the metadata directly.