app version to server (#7130)

- Send app version and release stage to collab on connect
- Read the new header on the server

Release Notes:

- Added the ability to collaborate with users on different releases of
Zed.

crates/collab/src/tests/test_server.rs

@@ -153,6 +153,7 @@ impl TestServer {
             }
             let settings = SettingsStore::test(cx);
             cx.set_global(settings);
+            release_channel::init("0.0.0", cx);
             client::init_settings(cx);
         });