genai: add debug log for _function_utils.py

[nobu007]

PR Description

genai: add debug log for _function_utils.py

logger.debug

• switch case branch info
• schema details

Type

🧹 Refactoring
✅ Test

Note(optional)

$ export LOG_LEVEL=DEBUG
$ python /home/jinno/git/drill/gamebook/test/test_struct
ured_output_joke.py
DEBUG:langchain_google_genai._function_utils:_format_to_gapic_function_declaration BaseModel
DEBUG:langchain_google_genai._function_utils:_convert_pydantic_to_genai_function
  schema={'description': 'Joke to tell user.', 'properties': {'setup': {'description': 'question to set up a joke', 'title': 'Setup', 'type': 'string'}, 'punchline': {'anyOf': [{'type': 'string'}, {'type': 'null'}], 'default': None, 'description': 'answer to resolve the joke', 'title': 'Punchline'}}, 'required': ['setup'], 'title': 'Joke', 'type': 'object'}