Add Gemini 3.5 Flash and 3.1 Flash-Lite to Gemini workflow block (#2355)

Adds two new model options to GEMINI_MODELS in the v3 block:

- gemini-3.5-flash (just released)
- gemini-3.1-flash-lite-preview

Both are marked as supporting thinking_level and native code execution
to match the rest of the Gemini 3.x family. Following the convention
established when Gemini 3 Flash Preview was added (#1910), only the v3
block is updated.

Author: Erol444

inference/core/workflows/core_steps/models/foundation/google_gemini/v3.py

@@ -50,12 +50,24 @@
 }
 
 GEMINI_MODELS = [
+    {
+        "id": "gemini-3.5-flash",
+        "name": "Gemini 3.5 Flash",
+        "supports_thinking_level": True,
+        "supports_native_code_execution": True,
+    },
     {
         "id": "gemini-3.1-pro-preview",
         "name": "Gemini 3.1 Pro",
         "supports_thinking_level": True,
         "supports_native_code_execution": True,
     },
+    {
+        "id": "gemini-3.1-flash-lite-preview",
+        "name": "Gemini 3.1 Flash-Lite",
+        "supports_thinking_level": True,
+        "supports_native_code_execution": True,
+    },
     {
         "id": "gemini-3-pro-preview",
         "name": "Gemini 3 Pro",