Add buffer integration test

Rearrange channel crate structure
Get channel buffer from database

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

crates/workspace/Cargo.toml

@@ -22,6 +22,7 @@ test-support = [
 db = { path = "../db" }
 call = { path = "../call" }
 client = { path = "../client" }
+channel = { path = "../channel" }
 collections = { path = "../collections" }
 context_menu = { path = "../context_menu" }
 drag_and_drop = { path = "../drag_and_drop" }

crates/workspace/src/workspace.rs

@@ -12,9 +12,10 @@ mod workspace_settings;
 
 use anyhow::{anyhow, Context, Result};
 use call::ActiveCall;
+use channel::ChannelStore;
 use client::{
     proto::{self, PeerId},
-    ChannelStore, Client, TypedEnvelope, UserStore,
+    Client, TypedEnvelope, UserStore,
 };
 use collections::{hash_map, HashMap, HashSet};
 use drag_and_drop::DragAndDrop;