Add context_over_200k for gemini-2.5-pro and adjust cache_read costs

https://ai.google.dev/gemini-api/docs/pricing#gemini-2.5-pro
https://cloud.google.com/vertex-ai/generative-ai/pricing#gemini-models-2.5 (rounds 0.125 to 0.13)

Author: rovo89

providers/google/models/gemini-2.5-pro.toml

@@ -13,7 +13,12 @@ open_weights = false
 [cost]
 input = 1.25
 output = 10.00
-cache_read = 0.31
+cache_read = 0.125
+
+[cost.context_over_200k]
+input = 2.50
+output = 15.00
+cache_read = 0.25
 
 [limit]
 context = 1_048_576