Added gitlab_tags helper to MLflow API

What does this MR do and why?

Related to [MLflow Compatibility]: allow users to pass ver... (#434408 - closed), this MR adds:

• The gitlab_tags API helper method to extract gitlab. tags to a special input hash
• The custom_version API helper method to return the version string when supplied as a gitlab tag (gitlab.version)
• The ability to persist the gitlab.version tag value as the version for a model version

How to set up and validate locally

1. In the Rails console, ensure the feature flags are enabled

   Feature.enable(:ml_experiment_tracking)
   Feature.enable(:model_registry)

2. In the Rails console, create an ML model in the project

   Ml::CreateModelService.new(Project.find(PROJECT_ID), 'my-model-name').execute

3. Enable the Model Registry feature toggle in the project by going to Settings > General > Visibility, project features, permissions and flipping the toggle for Model Registry

4. Use the following cURL command to create a new model version with a custom version string in a local GDK project

   curl -X "POST" "http://GDKHOST/api/v4/projects/PROJECT_ID/ml/mlflow/api/2.0/mlflow/model-versions/create" \
       -H 'Authorization: Bearer PERSONAL_ACCESS_TOKEN' \
       -H 'Content-Type: application/json; charset=utf-8' \
       -d $'{
     "name": "my-model-name",
     "tags": [
       {
         "key": "gitlab-version",
         "value": "4.5.6"
       }
     ],
     "description": "My Model Description"
   }'    

5. Use the get API to look up the newly created model version.

   curl -X "GET" "http://GDKHOST/api/v4/projects/PROJECT_ID/ml/mlflow/api/2.0/mlflow/model-versions/get?name=my-model-name&version=4.5.6" \
       -H 'Authorization: Bearer PERSONAL_ACCESS_TOKEN'    

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.