feat: add Spanner first-party toolset (breaking change to BigQueryTool, consolidating into generic GoogleTool)

Spanner toolset support basic operations to interact with Spanner table metadata and query results.

Consolidate BigQueryTool into generic GoogleTool, so that BigQueryToolset and SpannerToolset can share.

PiperOrigin-RevId: 794259782

tests/unittests/tools/spanner/test_spanner_credentials.py

@@ -0,0 +1,54 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from google.adk.tools.spanner.spanner_credentials import SpannerCredentialsConfig
+# Mock the Google OAuth and API dependencies
+import google.auth.credentials
+import google.oauth2.credentials
+import pytest
+
+
+class TestSpannerCredentials:
+  """Test suite for Spanner credentials configuration validation.
+
+  This class tests the credential configuration logic that ensures
+  either existing credentials or client ID/secret pairs are provided.
+  """
+
+  def test_valid_credentials_object_oauth2_credentials(self):
+    """Test that providing valid Credentials object works correctly with google.oauth2.credentials.Credentials.
+
+    When a user already has valid OAuth credentials, they should be able
+    to pass them directly without needing to provide client ID/secret.
+    """
+    # Create a mock oauth2 credentials object
+    oauth2_creds = google.oauth2.credentials.Credentials(
+        "test_token",
+        client_id="test_client_id",
+        client_secret="test_client_secret",
+        scopes=[],
+    )
+
+    config = SpannerCredentialsConfig(credentials=oauth2_creds)
+
+    # Verify that the credentials are properly stored and attributes are
+    # extracted
+    assert config.credentials == oauth2_creds
+    assert config.client_id == "test_client_id"
+    assert config.client_secret == "test_client_secret"
+    assert config.scopes == [
+        "https://www.googleapis.com/auth/spanner.data",
+    ]
+
+    assert config._token_cache_key == "spanner_token_cache"  # pylint: disable=protected-access