bedrock: Support global endpoints and new regional endpoints (#44103)

Closes #43598

Release Notes:

- bedrock: Added opt-in `allow_global` which enables global endpoints
- bedrock: Updated cross-region-inference endpoint and model list
- bedrock: Fixed Opus 4.5 access on Bedrock, now only accessible through the `allow_global` setting

crates/settings/src/settings_content/language_model.rs

@@ -61,6 +61,7 @@ pub struct AmazonBedrockSettingsContent {
     pub region: Option<String>,
     pub profile: Option<String>,
     pub authentication_method: Option<BedrockAuthMethodContent>,
+    pub allow_global: Option<bool>,
 }
 
 #[with_fallible_options]