feat: Add Gemini "Thinking" support to GoogleGenAIChatGenerator (#2212)

* Add GoogleGenAIChatGenerator thinking support

* Add thinking signatures

* PR feedback

* Test updated - PR review

* PR feedback - add more unit tests

* Expand coverage

Author: vblagoje

integrations/google_genai/pyproject.toml

@@ -26,7 +26,7 @@ classifiers = [
   "Programming Language :: Python :: Implementation :: CPython",
   "Programming Language :: Python :: Implementation :: PyPy",
 ]
-dependencies = ["haystack-ai>=2.16.1", "google-genai[aiohttp]>=1.17.0", "jsonref>=1.0.0"]
+dependencies = ["haystack-ai>=2.17.1", "google-genai[aiohttp]>=1.17.0", "jsonref>=1.0.0"]
 
 [project.urls]
 Documentation = "https://github.com/deepset-ai/haystack-core-integrations/tree/main/integrations/google_genai#readme"