Use configured HTTP transport for SSH metadata fetch (#5075)

## Summary
- `getServerMetadata` in `experimental/ssh` was using
`http.DefaultClient` for the driver proxy metadata request, bypassing
workspace TLS and proxy configuration from `client.Config`.
- Replace with `&http.Client{Transport: client.Config.HTTPTransport}` to
respect custom TLS certs and proxy settings.

## Test plan
- [ ] Verify SSH connect works with default config
- [ ] Verify SSH connect works behind corporate proxy with custom TLS
certs

Author: arsenyinfo

experimental/ssh/internal/client/client.go

@@ -454,7 +454,8 @@ func getServerMetadata(ctx context.Context, client *databricks.WorkspaceClient,
 	if err := client.Config.Authenticate(req); err != nil {
 		return 0, "", "", err
 	}
-	resp, err := http.DefaultClient.Do(req)
+	httpClient := &http.Client{Transport: client.Config.HTTPTransport}
+	resp, err := httpClient.Do(req)
 	if err != nil {
 		return 0, "", "", err
 	}