OpenAPI: Adapt the gobuild.yaml pipeline to run the new Go-OpenAPI generator

[manusa]

Description

Part of #6130

As part of the OpenAPI generation process, we've implemented functionality to generate the missing OpenAPI spec for types that aren't directly exposed by Kubernetes (#6131).

This process should run as part of the gobuild.yml pipeline to ensure that changes to this generator are persisted.

Tasks

• Add a new task in the global Makefile to generate-openapi
  • The task executes the build for the go project
• Rename the current generate-model task to generate-model-legacy
• Add a new task generate-model task that executes all of the model-related tasks (will now be generate-openapi & generate-model-legacy
• Modify the Check No Schema file modified step in the gobuild.yml pipeline to verify none of the files was modified.