🤖 feat: Add titling to Google client

[mungewrath]

Summary

Enables auto-generated titles when using Google models, as described in Issue 1422

Change Type

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update - see feat: Add titling to Google client LibreChat-AI/librechat.ai#45
• Translation update

Testing

• Tested with gemini-1.5-pro-latest
• Tested with gemini-pro
• Tested with invalid model name, and confirmed backend fails gracefully

Test Configuration:

Use GOOGLE_TITLE_MODEL environment variable in .env if desired to test specific model

Checklist

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have commented in any complex areas of my code
• I have made pertinent documentation changes
• My changes do not introduce new warnings
• Local unit tests pass with my changes
• A pull request for updating the documentation has been submitted.

[danny-avila]

Thanks for this. Will review and slate for v0.7.4. I was hoping to make use of Google's tool/functions for this, but I will see how well this works with vertex/gemini api