Create Google Generative AI Conversation integration (#93156)

* Copy openai_conversation to google_generative_ai_conversation
This is to improve diff of the next commit with the actual implementation.

Commands used:
cp -r homeassistant/components/openai_conversation/ homeassistant/components/google_generative_ai_conversation/
cp -r tests/components/openai_conversation/ tests/components/google_generative_ai_conversation/

find homeassistant/components/google_generative_ai_conversation/ tests/components/google_generative_ai_conversation/ -type f | xargs sed -i \
-e 's@openai_conversation@google_generative_ai_conversation@g' \
-e 's@OpenAI Conversation@Google Generative AI Conversation@g' \
-e 's@balloob@tronikos@g'

* Add google_generative_ai_conversation to Google brand

* Google Generative AI Conversation

* Sync recent openai changes

* handle empty responses

homeassistant/generated/integrations.json

@@ -2029,6 +2029,12 @@
           "iot_class": "cloud_polling",
           "name": "Google Domains"
         },
+        "google_generative_ai_conversation": {
+          "integration_type": "service",
+          "config_flow": true,
+          "iot_class": "cloud_polling",
+          "name": "Google Generative AI Conversation"
+        },
         "google_mail": {
           "integration_type": "service",
           "config_flow": true,