Replace Go model generation for openshift-model-operator

[manusa]

Description

Part of #6130

Replace model generation for openshift-model-operator module with new OpenAPI approach.

Note

For OpenShift models there are going to be multiple conflicts with the previously generated code.
The openapi-generator won't reuse some of the types since OpenShift's OpenAPI spec hasn't got shared references and model types are defined inline.

Tasks

• Remove build-helper-maven-plugin
• Remove maven-antrun-plugin from the generate profile
• Add openapi-model-generator-maven-plugin to the generate profile
• Configure the plugin to generate the specific classes
• Remove the go-related files and directories (Makefile, cmd)
• Remove invocation from the generateModel.sh script