Create ML model version GraphQL mutation

What does this MR do and why?

Create a new ML model version GraphQL mutation

Related to #462855 (closed)

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Before

How to set up and validate locally

1. Enable model registry and create a model in a project

Feature.enable(:model_registry)
project = Project.find(26)
model = Ml::CreateModelService.new(project, 'FooModel20').execute.payload
puts model.id

2. Use   http://gdk.test:3000/-/graphql-explorer and create some versions

mutation { mlModelVersionCreate(input: { projectPath: "g1/p2", modelId: "gid://gitlab/Ml::Model/20" }) {

modelVersion{
  version
  id
  _links {
    showPath
    importPath
  }
}
errors

} }

3. Navigate to project and see under Deploy menu, "model registry" the new version for your model 

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/assign me