Use scap library to implement screensharing on X11 (#27807)

While `scap` does have support for Wayland and Windows, but haven't seen
screensharing work properly there yet. So for now just adding support
for X11 screensharing.

WIP branches for enabling wayland and windows support:

* https://github.com/zed-industries/zed/tree/wayland-screenshare
* https://github.com/zed-industries/zed/tree/windows-screenshare


Release Notes:

- Added support for screensharing on X11 (Linux)

---------

Co-authored-by: Conrad <conrad@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Junkui Zhang <364772080@qq.com>

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

@@ -1,3 +1,4 @@
+use crate::platform::scap_screen_capture::scap_screen_sources;
 use core::str;
 use std::{
     cell::RefCell,
@@ -8,13 +9,13 @@ use std::{
     time::{Duration, Instant},
 };
 
+use anyhow::Context as _;
 use calloop::{
     EventLoop, LoopHandle, RegistrationToken,
     generic::{FdWrapper, Generic},
 };
-
-use anyhow::Context as _;
 use collections::HashMap;
+use futures::channel::oneshot;
 use http_client::Url;
 use smallvec::SmallVec;
 use util::ResultExt;
@@ -59,8 +60,8 @@ use crate::platform::{
 use crate::{
     AnyWindowHandle, Bounds, ClipboardItem, CursorStyle, DisplayId, FileDropEvent, Keystroke,
     Modifiers, ModifiersChangedEvent, MouseButton, Pixels, Platform, PlatformDisplay,
-    PlatformInput, Point, RequestFrameOptions, ScaledPixels, ScrollDelta, Size, TouchPhase,
-    WindowParams, X11Window, modifiers_from_xinput_info, point, px,
+    PlatformInput, Point, RequestFrameOptions, ScaledPixels, ScreenCaptureSource, ScrollDelta,
+    Size, TouchPhase, WindowParams, X11Window, modifiers_from_xinput_info, point, px,
 };
 
 /// Value for DeviceId parameters which selects all devices.
@@ -1327,6 +1328,16 @@ impl LinuxClient for X11Client {
         ))
     }
 
+    fn is_screen_capture_supported(&self) -> bool {
+        true
+    }
+
+    fn screen_capture_sources(
+        &self,
+    ) -> oneshot::Receiver<anyhow::Result<Vec<Box<dyn ScreenCaptureSource>>>> {
+        scap_screen_sources(&self.0.borrow().common.foreground_executor)
+    }
+
     fn open_window(
         &self,
         handle: AnyWindowHandle,