Create custom container training job function: `gcva_custom_container_training_job()`

[justinjm]

summary

Create a TrainingPipeline that runs a CustomJob and imports the resulting artifacts as a Model.

Docs:

• Create training pipelines  |  Vertex AI  |  Google Cloud ("Use the following code sample to create a training pipeline using the create method of the trainingPipeline resource.")

API:

• REST Resource: projects.locations.trainingPipelines  |  Vertex AI  |  Google Cloud

example (via reticulate):

• blog: https://cloud.google.com/blog/products/ai-machine-learning/train-and-deploy-ml-models-with-r-and-plumber-on-vertex-ai
• code: https://github.com/GoogleCloudPlatform/vertex-ai-samples/blob/main/notebooks/community/ml_ops/stage2/get_started_vertex_training_r_using_r_kernel.ipynb