agent: Allow customizing temperature by provider/model (#30033)

Adds a new `agent.model_parameters` setting that allows the user to
specify a custom temperature for a provider AND/OR model:

```json5
    "model_parameters": [
      // To set parameters for all requests to OpenAI models:
      {
        "provider": "openai",
        "temperature": 0.5
      },
      // To set parameters for all requests in general:
      {
        "temperature": 0
      },
      // To set parameters for a specific provider and model:
      {
        "provider": "zed.dev",
        "model": "claude-3-7-sonnet-latest",
        "temperature": 1.0
      }
    ],
```

Release Notes:

- agent: Allow customizing temperature by provider/model

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>
Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/language_models/src/settings.rs

@@ -87,8 +87,8 @@ pub struct AllLanguageModelSettingsContent {
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, JsonSchema)]
 #[serde(untagged)]
 pub enum AnthropicSettingsContent {
-    Legacy(LegacyAnthropicSettingsContent),
     Versioned(VersionedAnthropicSettingsContent),
+    Legacy(LegacyAnthropicSettingsContent),
 }
 
 impl AnthropicSettingsContent {
@@ -197,8 +197,8 @@ pub struct MistralSettingsContent {
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, JsonSchema)]
 #[serde(untagged)]
 pub enum OpenAiSettingsContent {
-    Legacy(LegacyOpenAiSettingsContent),
     Versioned(VersionedOpenAiSettingsContent),
+    Legacy(LegacyOpenAiSettingsContent),
 }
 
 impl OpenAiSettingsContent {