Add the latest stable Gemini models

[KingXMAX]

The latest Gemini models have been finally released:
Gemini 2.5 Pro (Not Preview anymore)
Gemini 2.5 Flash (Finally Stable)
Here is the docs page that contains all info you need to add the models successfully:
https://ai.google.dev/gemini-api/docs/models
Thank you.

[sceuick]

If you use Google AI provider, the model list will update automatically.