Remove dependents of language_models (#25511)

This PR removes the dependents of the `language_models` crate.

The following types have been moved from `language_models` to
`language_model` to facilitate this:

- `LlmApiToken`
- `RefreshLlmTokenListener`
- `MaxMonthlySpendReachedError`
- `PaymentRequiredError`

With this change only `zed` now depends on `language_models`.

Release Notes:

- N/A

crates/language_models/src/language_models.rs

@@ -11,8 +11,6 @@ mod settings;
 
 use crate::provider::anthropic::AnthropicLanguageModelProvider;
 use crate::provider::cloud::CloudLanguageModelProvider;
-pub use crate::provider::cloud::LlmApiToken;
-pub use crate::provider::cloud::RefreshLlmTokenListener;
 use crate::provider::copilot_chat::CopilotChatLanguageModelProvider;
 use crate::provider::google::GoogleLanguageModelProvider;
 use crate::provider::lmstudio::LmStudioLanguageModelProvider;
@@ -37,8 +35,6 @@ fn register_language_model_providers(
 ) {
     use feature_flags::FeatureFlagAppExt;
 
-    RefreshLlmTokenListener::register(client.clone(), cx);
-
     registry.register_provider(
         AnthropicLanguageModelProvider::new(client.http_client(), cx),
         cx,