feat: batch prediction samples

[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

[gryczj]

Samples based on GoogleCloudPlatform/java-docs-samples@5cb4201 and GoogleCloudPlatform/java-docs-samples#9519

[snippet-bot]

Here is the summary of changes.

You are about to add 2 region tags.

• ai-platform/snippets/batch-code-predict.js:20, tag generativeaionvertexai_batch_code_predict
• ai-platform/snippets/batch-text-predict.js:20, tag generativeaionvertexai_batch_text_predict

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