Add DNS Resolution to gsutil -D Debug Output

Currently, the `gsutil -D` debug output shows the hostname (e.g., `storage.googleapis.com`) used for accessing Google Cloud Storage resources. However, it doesn't provide the resolved IP address. This information would be valuable for troubleshooting, particularly in scenarios where:

- **Private Service Connect endpoints are used:** We need to confirm if the connection is going to the expected private IP address.
- **Network issues are suspected:** Knowing the resolved IP can help in diagnosing network connectivity problems.

**Suggested Enhancement:**

Include the resolved IP address(es) in the gsutil -D output, potentially like this:

`[DEBUG] Using endpoint: storage.googleapis.com (resolved to 142.250.185.206) `

This enhancement would improve the debugging experience for users working with complex network setups or those needing deeper insights into gsutil's network behavior.

Start at the gsutil -D debug-output entry point and trace where the endpoint hostname is emitted. Identify the existing network-resolution path, then verify that debug output reports the resolved IP address or addresses for the endpoint.

Written by the indexing model from the issue text.