cli: implement better self-updating

- Start separating a "standalone" CLI. This is a little awkward with clap-
  derive, but I got it working. Detection of whether the CLI _is_
  standalone is still todo.
- Remove the old ad-hoc update code for code-server, and use the update
  service instead.
- Fix some of the "permission denied" errors people got while updating
  before. We need to rename the old running binary, not just overwrite it.

cli/src/desktop/version_manager.rs

@@ -265,6 +265,7 @@ async fn get_release_for_request(
 			platform,
 			commit: commit.clone(),
 			quality: *quality,
+			name: "".to_string(),
 			target: TargetKind::Archive,
 		}),
 		RequestedVersion::Quality(quality) => update_service