feat(tpu): add tpu vm stop/start samples.

[TetyanaYahodska]

Description

Documentation - https://cloud.google.com/tpu/docs/managing-tpus-tpu-vm
Sample in Python GoogleCloudPlatform/python-docs-samples#12702
Fixes #

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

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 2 region tags.

• tpu/src/main/java/tpu/StartTpuVm.java:19, tag tpu_vm_start
• tpu/src/main/java/tpu/StopTpuVm.java:19, tag tpu_vm_stop

---

This comment is generated by snippet-bot.
If you find problems with this result, please file an issue at:
https://github.com/googleapis/repo-automation-bots/issues.
To update this comment, add snippet-bot:force-run label or use the checkbox below:

• Refresh this comment

[minherz]

looks good. thank you.

to resolve the conflict caused by merging #9606 please rebase the branch before merging.