feat: add tpu_vm_create_topology/startup_script

[gryczj]

Description

Fixes #

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Checklist

• I have followed guidelines from CONTRIBUTING.MD and Samples Style Guide
• Tests pass: npm test (see Testing)
• Lint pass: npm run lint (see Style)
• 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)
• This pull request is from a branch created directly off of GoogleCloudPlatform/nodejs-docs-samples. Not a fork.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample
• This sample adds a new sample directory, and I created GitHub Actions workflow 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/createStartupScriptVM.js:20, tag tpu_vm_create_startup_script
• tpu/createTopologyVM.js:20, tag tpu_vm_create_topology

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[gryczj]

From time to time there is an issue with Enforcer when running the tests, but it is not related to the implementation.
GoogleError: GCE Enforcer is deleting necessary Cloud TPU infrastructure resources in this project. Please opt out of GCE Enforcer for this project. [FIREWALLS is deleted]

[gryczj]

Due to high costs of TPU Nodes, it was decided to use mocks in the tests.