Add support to x-codeSamples in v3

[lucasassisrosa]

Description

This PR aims to fix the x-codeSamples integration. When x-codeSamples are provided, add as a variant for the target supported language in the API Explorer. At first it seems that the code was aiming to only display the custom code sample when x-codeSamples is provided. I assumed it's better to add the custom code samples to the existing generated code samples in the list of variants

Motivation and Context

x-codeSamples redoc extension was partially supported and breaking the rendering if loaded in API Explorer. Continues #589 (@joecrop I tried to continue the implementation but the codebase has changed considerably)

How Has This Been Tested?

Go to http://localhost:3000/petstore/add-pet and check API Explorer code samples. It reflects the OpenAPI spec now on x-codeSamples, following syntax highlighting

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes if appropriate.
• All new and existing tests passed.

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