remote projects per user (#10594)

Release Notes:

- Made remote projects per-user instead of per-channel. If you'd like to
be part of the remote development alpha, please email hi@zed.dev.

---------

Co-authored-by: Bennet Bo Fenner <53836821+bennetbo@users.noreply.github.com>
Co-authored-by: Bennet <bennetbo@gmx.de>
Co-authored-by: Nate Butler <1714999+iamnbutler@users.noreply.github.com>
Co-authored-by: Nate Butler <iamnbutler@gmail.com>

crates/collab/src/tests/integration_tests.rs

@@ -3743,6 +3743,10 @@ async fn test_leaving_project(
 
     buffer_b2.read_with(cx_b, |buffer, _| assert_eq!(buffer.text(), "a-contents"));
 
+    project_a.read_with(cx_a, |project, _| {
+        assert_eq!(project.collaborators().len(), 2);
+    });
+
     // Drop client B's connection and ensure client A and client C observe client B leaving.
     client_b.disconnect(&cx_b.to_async());
     executor.advance_clock(RECONNECT_TIMEOUT);