Sri Varshitha f2d9e3b579 feat(tools/alloydb-get-instance): Add get-instance tool for alloydb (#1435) ...

## Description

---
This pull request introduces a new custom tool kind
`alloydb-get-instance` that retrieves detailed information for a
specific AlloyDB instance.

### Example Configuration

```yaml
tools:
  get_instance:
    kind: alloydb-get-instance
    source: alloydb-admin-source
    description: Use this tool to retrieve detailed information for a specific AlloyDB instance.
```

### Example Request
``` 
curl -X POST http://127.0.0.1:5000/api/tool/get_instance/invoke \
-H "Content-Type: application/json" \
-d '{
    "projectId": "example-project",
    "locationId": "us-central1",
    "clusterId": "my-alloydb-cluster",
    "instanceId": "my-alloydb-instance",
}'
```

## PR Checklist

---
> Thank you for opening a Pull Request! Before submitting your PR, there
are a
> few things you can do to make sure it goes smoothly:

- [x] Make sure you reviewed

[CONTRIBUTING.md](https://github.com/googleapis/genai-toolbox/blob/main/CONTRIBUTING.md)
- [ ] Make sure to open an issue as a

[bug/issue](https://github.com/googleapis/genai-toolbox/issues/new/choose)
before writing your code! That way we can discuss the change, evaluate
  designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)
- [x] Make sure to add `!` if this involve a breaking change

🛠️ Fixes #<issue_number_goes_here>

2025-09-16 11:13:03 +05:30

..

en

feat(tools/alloydb-get-instance): Add get-instance tool for alloydb (#1435)

2025-09-16 11:13:03 +05:30