fix(google-genai): Set agent name (#5038)

### Description
Cherry-picked off of
#5030

#### Issues
Ref
https://linear.app/getsentry/issue/TET-1293/make-sure-that-agent-name-is-set-on-all-of-its-gen-ai-children

#### Reminders
- Please add tests to validate your changes, and lint your code using
`tox -e linters`.
- Add GH Issue ID _&_ Linear ID (if applicable)
- PR title should use [conventional
commit](https://develop.sentry.dev/engineering-practices/commit-messages/#type)
style (`feat:`, `fix:`, `ref:`, `meta:`)
- For external contributors:
[CONTRIBUTING.md](https://github.com/getsentry/sentry-python/blob/master/CONTRIBUTING.md),
[Sentry SDK development docs](https://develop.sentry.dev/sdk/), [Discord
community](https://discord.gg/Ww9hbqr)

---------

Co-authored-by: Fabian Schindler <[email protected]>

Author: 2 people

sentry_sdk/integrations/google_genai/__init__.py

@@ -92,6 +92,7 @@ def new_generate_content_stream(self, *args, **kwargs):
         chat_span.set_data(SPANDATA.GEN_AI_REQUEST_MODEL, model_name)
         set_span_data_for_request(chat_span, integration, model_name, contents, kwargs)
         chat_span.set_data(SPANDATA.GEN_AI_RESPONSE_STREAMING, True)
+        chat_span.set_data(SPANDATA.GEN_AI_AGENT_NAME, model_name)
 
         try:
             stream = f(self, *args, **kwargs)
@@ -165,6 +166,7 @@ async def new_async_generate_content_stream(self, *args, **kwargs):
         chat_span.set_data(SPANDATA.GEN_AI_REQUEST_MODEL, model_name)
         set_span_data_for_request(chat_span, integration, model_name, contents, kwargs)
         chat_span.set_data(SPANDATA.GEN_AI_RESPONSE_STREAMING, True)
+        chat_span.set_data(SPANDATA.GEN_AI_AGENT_NAME, model_name)
 
         try:
             stream = await f(self, *args, **kwargs)
@@ -233,6 +235,7 @@ def new_generate_content(self, *args, **kwargs):
                 chat_span.set_data(SPANDATA.GEN_AI_OPERATION_NAME, "chat")
                 chat_span.set_data(SPANDATA.GEN_AI_SYSTEM, GEN_AI_SYSTEM)
                 chat_span.set_data(SPANDATA.GEN_AI_REQUEST_MODEL, model_name)
+                chat_span.set_data(SPANDATA.GEN_AI_AGENT_NAME, model_name)
                 set_span_data_for_request(
                     chat_span, integration, model_name, contents, kwargs
                 )