Gold tests for utils

[bobhancockg]

…v19 compatibility

This commit introduces a test suite for the utility modules located in the examples/utils/ directory.

Key changes:

• Created a new test directory: examples/utils/tests/.
• Added examples/utils/tests/__init__.py.
• Added examples/utils/tests/test_example_helpers.py with unit tests for get_printable_datetime and get_image_bytes_from_url using the unittest framework and unittest.mock.
• Verified that the existing google-ads client library (v26.1.0) already supports Google Ads API v19, so no direct dependency changes for API versioning were required.
• Updated noxfile.py: Modified the TEST_COMMAND for unittest discover to scan from the project root (-s .) instead of just the top-level tests directory. This ensures the new tests in examples/utils/tests/ are discovered and executed by the standard nox testing sessions.
• Adjusted the import statement in test_example_helpers.py to from examples.utils import example_helpers to ensure correct module resolution when tests are run from the project root.