feat: add Google Gemini API support (#1418)

* feat: add Google Gemini API support

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* fix: remove unused imports

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* feat: add google-genai dependency

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* fix: update Gemini API implementation to use correct API methods

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* refactor: improve Gemini API implementation based on official documentation

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* fix: remove unsupported timeout parameter from Gemini API implementation

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* fix: correct Gemini API implementation based on official documentation

Co-Authored-By: Junyan Qin <Chin> <rockchinq@gmail.com>

* feat: update geminichatcmpl

* deps: add google-generativeai

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: Junyan Qin <Chin> <rockchinq@gmail.com>

pkg/provider/modelmgr/requesters/gemini.svg

@@ -0,0 +1 @@
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