feat: Add metadata SDK samples for list artifact and list execution

[SinaChavoshi]

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Fixes #<issue_number_goes_here> 🦕

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• samples/model-builder/experiment_tracking/list_artifact_sample.py:20, tag aiplatform_sdk_create_artifact_with_sdk_sample
• samples/model-builder/experiment_tracking/list_execution_sample.py:20, tag aiplatform_sdk_create_execution_with_sdk_sample

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