Have the configuration page display google console projects and vertex AI data stores

Going to take a shot at this again.

From @swirt:

Keep it simple, display a list with instructions to copy paste the values you want into the field.

This is ready for review, from my research last year and right now I think only data stores can be looked up with a service account and project ID + location. I think project ID could be loaded from the service account file path but probably not useful?

The current MR is ready to review. QA steps:

1. Use the tugboat URL or a local instance with the merge request branch
2. Enable vertex ai search if not enabled
3. Create a new search page from /admin/config/search/pages
4. Fill in the Service Account Credentials, Google Cloud Project ID, and change the location if it not set to global
5. Click the button 'Lookup Data Stores'
6. Confirm you see a list of data stores for the project ID and location
7. Copy the ID and save it in the Vertex AI Data Store ID field
8. Save the rest of the values like usual
9. Confirm the search works as expected

timozura → credited swirt → .

Tested on a fresh site and on an established site. Nice approach. Ran into no issues so I merged it.