clean models manager (#9168)

Have only the following Methods:
- `list_models`: getting current available models
- `try_list_models`: sync version no refresh for tui use
- `get_default_model`: get the default model (should be tightened to
core and received on session configuration)
- `get_model_info`: get `ModelInfo` for a specific model (should be
tightened to core but used in tests)
- `refresh_if_new_etag`: trigger refresh on different etags

Also move the cache to its own struct

codex-rs/core/src/thread_manager.rs

@@ -138,8 +138,15 @@ impl ThreadManager {
         self.state.models_manager.clone()
     }
 
-    pub async fn list_models(&self, config: &Config) -> Vec<ModelPreset> {
-        self.state.models_manager.list_models(config).await
+    pub async fn list_models(
+        &self,
+        config: &Config,
+        refresh_strategy: crate::models_manager::manager::RefreshStrategy,
+    ) -> Vec<ModelPreset> {
+        self.state
+            .models_manager
+            .list_models(config, refresh_strategy)
+            .await
     }
 
     pub async fn list_thread_ids(&self) -> Vec<ThreadId> {