Move report_assistant_event into language_model crate (#25508)

This PR moves the `report_assistant_event` function from the
`language_models` crate to the `language_model` crate.

This allows us to drop some dependencies on `language_models`.

Release Notes:

- N/A

crates/assistant2/src/terminal_codegen.rs

@@ -2,8 +2,7 @@ use crate::inline_prompt_editor::CodegenStatus;
 use client::telemetry::Telemetry;
 use futures::{channel::mpsc, SinkExt, StreamExt};
 use gpui::{App, AppContext as _, Context, Entity, EventEmitter, Task};
-use language_model::{LanguageModelRegistry, LanguageModelRequest};
-use language_models::report_assistant_event;
+use language_model::{report_assistant_event, LanguageModelRegistry, LanguageModelRequest};
 use std::{sync::Arc, time::Instant};
 use telemetry_events::{AssistantEvent, AssistantKind, AssistantPhase};
 use terminal::Terminal;