Add integration tests for validate API product swagger definition

[SavinduDimal]

Purpose

• Add integration tests for validate API product swagger definition.
• Related PRs: Add missing references to api product swagger definition carbon-apimgt#12159

Approach

• Create an API with a swagger definition which has path parameters defined as $ref in path level and response headers defined as $ref
• Create an API product with that API and validate the API definition of that API product

[SavinduDimal]

Merging the PR since,

• Add missing references to api product swagger definition carbon-apimgt#12159 was merged.
• WSO2 API Manager - Based on product backend Test Module has passed.
• Github check failed due to WSO2 API Manager - Based on product restart Test Module failure caused by Unable to start carbon server on port 10263 : Port already in use