Linux: Rewrite the event loop using calloop (#8314)

This PR unifies the event loop code for Wayland and X11. On Wayland,
blocking dispatch is now used. On X11, the invisible window is no longer
needed.

Release Notes:

- N/A

---------

Co-authored-by: Dzmitry Malyshau <kvark@fastmail.com>
Co-authored-by: Tadeo Kondrak <me@tadeo.ca>
Co-authored-by: Mikayla Maki <mikayla@zed.dev>
Co-authored-by: julia <julia@zed.dev>

crates/gpui/src/platform/linux.rs

@@ -1,5 +1,4 @@
 mod client;
-mod client_dispatcher;
 mod dispatcher;
 mod platform;
 mod text_system;
@@ -10,4 +9,4 @@ mod x11;
 pub(crate) use dispatcher::*;
 pub(crate) use platform::*;
 pub(crate) use text_system::*;
-pub(crate) use x11::*;
+// pub(crate) use x11::*;