Set override_redirect for PopUps (#42224)

Currently on x11, gpui PopUp windows only rely on the "notification"
type in order to indicate that they should spawn as floating window.
Several window managers (leftwm in my case, but it also seems to be the
case for dwm and ratpoison) do not this property into account thus not
spawning them as float. On the other hand, using Floating instead of
PopUp do make those windows spawn as floating, as these window manager
do take into account the (older) "dialog" type.

The [freedekstop
documentation](https://specifications.freedesktop.org/wm/1.5/ar01s05.html#id-1.6.7)
does seem to suggest that these windows should also have the override
redirect property :
> This property is typically used on override-redirect windows. 

Note that this also disables pretty much all interactions with the
window manager (such as moving the window, resizing etc...)

Release Notes:

- Fix popup windows not spawning floating sometime on x11

crates/gpui/src/platform/linux/x11/window.rs

@@ -431,6 +431,7 @@ impl X11WindowState {
             // https://stackoverflow.com/questions/43218127/x11-xlib-xcb-creating-a-window-requires-border-pixel-if-specifying-colormap-wh
             .border_pixel(visual_set.black_pixel)
             .colormap(colormap)
+            .override_redirect((params.kind == WindowKind::PopUp) as u32)
             .event_mask(
                 xproto::EventMask::EXPOSURE
                     | xproto::EventMask::STRUCTURE_NOTIFY