feat(tpu): add tpu vm create spot sample.

[TetyanaYahodska]

Description

Documentation - https://cloud.google.com/tpu/docs/spot
Sample in Python - GoogleCloudPlatform/python-docs-samples#12719
Fixes #

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Checklist

• I have followed Sample Format Guide
• pom.xml parent set to latest shared-configuration
• Appropriate changes to README are included in PR
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Tests pass: mvn clean verify required
• Lint passes: mvn -P lint checkstyle:check required
• Static Analysis: mvn -P lint clean compile pmd:cpd-check spotbugs:check advisory only
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new Product API, and I updated the Blunderbuss issue/PR auto-assigner with the codeowners for this sample
• Please merge this PR for me once it is approved

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• tpu/src/main/java/tpu/CreateSpotTpuVm.java:19, tag tpu_vm_create_spot

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