Python: Temporarily xFail some google ai integration tests to unblock

[TaoChenOSU]

Motivation and Context

This pull request includes updates to the test cases in the python/tests/integration/completions/test_chat_completion_with_function_calling.py and python/tests/integration/completions/test_chat_completion_with_image_input_text_output.py files. The changes primarily address the handling of Google AI API issues by adding markers to the tests.

Description

• python/tests/integration/completions/test_chat_completion_with_function_calling.py: Added xfail markers to multiple test cases to handle temporary failures due to Google AI API issues related to function calling not being enabled for models/gemini-1.5-flash. [1] [2] [3]
• python/tests/integration/completions/test_chat_completion_with_image_input_text_output.py: Added an xfail marker to handle temporary failure due to Google AI API issues related to image input modality not being enabled for models/gemini-1.5-flash.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[esttenorio]