feat(genai): tools vais sample

[Guiners]

Description

Add a new GenAI Vertex AI Search tool sample.

• Test is running locally fine.

• To make this test work locally for me and my project, I use:
  const DATASTORE =
  'projects/cloud-ai-devrel-softserve/locations/global/collections/default_collection/dataStores/example-adk-website-datastore_1755611010401';
  from file tools-vais-with-txt.

• To make the test look and work the same as in the Python sample, it is used:
  const datastore = projects/${projectId}/locations/global/collections/default_collection/dataStores/grounding-test-datastore;
  from tools-vais-with-txt.test.

IMO, the project that is used to run the test is missing a resource from above. Adding it should fix it.

• To make the Vertex AI Search tool with text sample work locally, a datastore had to be created, and the Discovery Engine Editor role was required. This means the pipeline will fail without them.
• For reference, for this test, I used the same datastore that is used in the corresponding Python sample: projects/{PROJECT_ID}/locations/global/collections/default_collection/dataStores/grounding-test-datastore

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)
• Required CI tests pass (see CI testing)
• Please merge this PR for me once it is approved

Note: Any check with (dev), (experimental), or (legacy) can be ignored and should not block your PR from merging (see CI testing).

[snippet-bot]

Here is the summary of changes.

You are about to add 1 region tag.

• genai/tools/tools-vais-with-txt.js:17, tag googlegenaisdk_tools_vais_with_txt

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[msampathkumar]

LGTM