X11: Continuous Presentation (#7762)

Alternative to #7758, which doesn't involve adding a new trait method
`request_draw`.
Somehow, my whole screen goes blinking black with this when moving the
window, so not ready for landing.

Release Notes:
- N/A

---------

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

crates/gpui/src/gpui.rs

@@ -61,6 +61,7 @@
 
 #![deny(missing_docs)]
 #![allow(clippy::type_complexity)]
+#![allow(clippy::collapsible_else_if)]
 
 #[macro_use]
 mod action;