Consolidate logic for protobuf message handling between ssh and web socket clients (#17185)

This is a refactor to prepare for adding LSP support in SSH remote
projects.

Release Notes:

- N/A

---------

Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Conrad <conrad@zed.dev>

crates/channel/src/channel_buffer.rs

@@ -5,7 +5,7 @@ use collections::HashMap;
 use gpui::{AppContext, AsyncAppContext, Context, EventEmitter, Model, ModelContext, Task};
 use language::proto::serialize_version;
 use rpc::{
-    proto::{self, PeerId},
+    proto::{self, AnyProtoClient, PeerId},
     TypedEnvelope,
 };
 use std::{sync::Arc, time::Duration};
@@ -14,7 +14,7 @@ use util::ResultExt;
 
 pub const ACKNOWLEDGE_DEBOUNCE_INTERVAL: Duration = Duration::from_millis(250);
 
-pub(crate) fn init(client: &Arc<Client>) {
+pub(crate) fn init(client: &AnyProtoClient) {
     client.add_model_message_handler(ChannelBuffer::handle_update_channel_buffer);
     client.add_model_message_handler(ChannelBuffer::handle_update_channel_buffer_collaborators);
 }