:adhesive_bandage: Add google search retrieval as builtin tool

[Grogdunn]

trafficstars

Added in Vertex client configuration the possibility to use GoogleSearchRetrieval as tool as grounding feature

https://cloud.google.com/vertex-ai/generative-ai/docs/model-reference/grounding

next up (on other PR) grounding support with "retrieval" tool, more studies needed.

[Grogdunn]

aligned with main

[markpollack]

merged in 793052c2e96cf95230ddd8f7bbcb535abdffa397

I had a bad merge conflict somehow and ended up redoing the changes and adding a test on another branch. Sorry I forgot to add your name in the commit message. next time! ;)