docs(samples): add Model Registry samples to Vertex AI Python SDK

[inardini]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[snippet-bot]

Here is the summary of changes.

You are about to add 13 region tags.

• samples/model-builder/model_registry/assign_aliases_model_version_sample.py:15, tag aiplatform_model_registry_assign_aliases_model_version_sample
• samples/model-builder/model_registry/create_aliased_model_sample.py:15, tag aiplatform_model_registry_create_aliased_model_sample
• samples/model-builder/model_registry/create_default_model_sample.py:15, tag aiplatform_model_registry_create_default_model_sample
• samples/model-builder/model_registry/create_model_registry_sample.py:15, tag aiplatform_model_registry_create_model_registry_sample
• samples/model-builder/model_registry/delete_aliases_model_version_sample.py:15, tag aiplatform_model_registry_delete_aliases_model_version_sample
• samples/model-builder/model_registry/delete_model_sample.py:15, tag aiplatform_model_registry_delete_model_sample
• samples/model-builder/model_registry/delete_model_version_sample.py:15, tag aiplatform_model_registry_delete_model_version_sample
• samples/model-builder/model_registry/get_model_version_info_sample.py:15, tag aiplatform_model_registry_get_model_version_info_sample
• samples/model-builder/model_registry/get_registered_model_version_sample.py:15, tag aiplatform_model_registry_get_registered_model_version_sample
• samples/model-builder/model_registry/list_model_versions_with_model_registry_sample.py:15, tag aiplatform_model_registry_list_model_versions_with_model_registry_sample
• samples/model-builder/model_registry/upload_new_aliased_model_version_sample.py:15, tag aiplatform_model_registry_upload_new_aliased_model_version_sample
• samples/model-builder/model_registry/upload_new_default_model_version_sample.py:15, tag aiplatform_model_registry_upload_new_default_model_version_sample
• samples/model-builder/model_registry/upload_new_model_version_using_custom_training_pipeline_sample.py:15, tag aiplatform_model_registry_upload_new_model_version_using_custom_training_pipeline

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[engelke]

Please fix all test failures (only lint ones are showing so far) before PR can be merged.