Add buffer integration test

Rearrange channel crate structure
Get channel buffer from database

co-authored-by: Max <max@zed.dev>

crates/zed/Cargo.toml

@@ -21,6 +21,7 @@ activity_indicator = { path = "../activity_indicator" }
 auto_update = { path = "../auto_update" }
 breadcrumbs = { path = "../breadcrumbs" }
 call = { path = "../call" }
+channel = { path = "../channel" }
 cli = { path = "../cli" }
 collab_ui = { path = "../collab_ui" }
 collections = { path = "../collections" }

crates/zed/src/main.rs

@@ -3,13 +3,12 @@
 
 use anyhow::{anyhow, Context, Result};
 use backtrace::Backtrace;
+use channel::ChannelStore;
 use cli::{
     ipc::{self, IpcSender},
     CliRequest, CliResponse, IpcHandshake, FORCE_CLI_MODE_ENV_VAR_NAME,
 };
-use client::{
-    self, ChannelStore, TelemetrySettings, UserStore, ZED_APP_VERSION, ZED_SECRET_CLIENT_TOKEN,
-};
+use client::{self, TelemetrySettings, UserStore, ZED_APP_VERSION, ZED_SECRET_CLIENT_TOKEN};
 use db::kvp::KEY_VALUE_STORE;
 use editor::{scroll::autoscroll::Autoscroll, Editor};
 use futures::{