Linux window decorations (#13611)

This PR adds support for full client side decorations on X11 and Wayland

TODO:
- [x] Adjust GPUI APIs to expose CSD related information
- [x] Implement remaining CSD features (Resizing, window border, window
shadow)
- [x] Integrate with existing background appearance and window
transparency
- [x] Figure out how to check if the window is tiled on X11
- [x] Implement in Zed
- [x] Repeatedly maximizing and unmaximizing can panic
- [x] Resizing is strangely slow
- [x] X11 resizing and movement doesn't work for this:
https://discord.com/channels/869392257814519848/1204679850208657418/1256816908519604305
- [x] The top corner can clip with current styling
- [x] Pressing titlebar buttons doesn't work
- [x] Not showing maximize / unmaximize buttons
- [x] Noisy transparency logs / surface transparency problem
https://github.com/zed-industries/zed/pull/13611#issuecomment-2201685030
- [x] Strange offsets when dragging the project panel
https://github.com/zed-industries/zed/pull/13611#pullrequestreview-2154606261
- [x] Shadow inset with `_GTK_FRAME_EXTENTS` doesn't respect tiling on
X11 (observe by snapping an X11 window in any direction)

Release Notes:

- N/A

---------

Co-authored-by: conrad <conrad@zed.dev>
Co-authored-by: Owen Law <81528246+someone13574@users.noreply.github.com>
Co-authored-by: apricotbucket28 <71973804+apricotbucket28@users.noreply.github.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/theme/src/theme.rs

@@ -28,7 +28,8 @@ pub use settings::*;
 pub use styles::*;
 
 use gpui::{
-    AppContext, AssetSource, Hsla, SharedString, WindowAppearance, WindowBackgroundAppearance,
+    px, AppContext, AssetSource, Hsla, Pixels, SharedString, WindowAppearance,
+    WindowBackgroundAppearance,
 };
 use serde::Deserialize;
 
@@ -38,6 +39,9 @@ pub enum Appearance {
     Dark,
 }
 
+pub const CLIENT_SIDE_DECORATION_ROUNDING: Pixels = px(10.0);
+pub const CLIENT_SIDE_DECORATION_SHADOW: Pixels = px(10.0);
+
 impl Appearance {
     pub fn is_light(&self) -> bool {
         match self {