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/zed/src/zed.rs

@@ -4237,7 +4237,7 @@ mod tests {
                 cx,
             );
             image_viewer::init(cx);
-            language_model::init(cx);
+            language_model::init(app_state.client.clone(), cx);
             language_models::init(
                 app_state.user_store.clone(),
                 app_state.client.clone(),