ci: Update workflows for ai/ml/data to use labeled on pull_request trigger

[grayside]

Description

Scoped to Samples workflows for products in ai-platform, generativeai, dataproc, datalabeling, datacatalog, dlp.

This grouping is trying to find data-intensive tests that take a long time to process so remaining changes have more even test completion times.

Implementation of #3747, sibling of #3748.

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

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

[grayside]

The errors in these failing tests appear to be non-transient: I'm seeing bugs coming from samples and/or tests. As out of scope bugs, they should be non-blocking for this PR.