Revert "Use scap library to implement screensharing on X11 (#27807)" (#28141)

This reverts commit c2afc2271b.

Build on ARM if failing, likely because `c_char` is `u8` on arm and `i8`
on x86:

```
error[E0308]: mismatched types
   --> /home/runner/.cargo/git/checkouts/scap-40ad33e1dd47aaea/5715067/src/targets/linux/mod.rs:75:74
    |
75  |     let result = unsafe { XmbTextPropertyToTextList(display, &mut xname, &mut list, &mut count) };
    |                           -------------------------                      ^^^^^^^^^ expected `*mut *mut *mut u8`, found `&mut *mut *mut i8`
    |                           |
    |                           arguments to this function are incorrect
    |
    = note:    expected raw pointer `*mut *mut *mut u8`
            found mutable reference `&mut *mut *mut i8`
note: function defined here
   --> /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/x11-2.21.0/src/xlib.rs:552:10
    |
552 |   pub fn XmbTextPropertyToTextList (_4: *mut Display, _3: *const XTextProperty, _2: *mut *mut *mut c_char, _1: *mut c_int) -> c_int,
    |          ^^^^^^^^^^^^^^^^^^^^^^^^^
```

Release Notes:

- N/A

crates/gpui/src/platform.rs

@@ -26,12 +26,6 @@ mod test;
 #[cfg(target_os = "windows")]
 mod windows;
 
-#[cfg(all(
-    any(target_os = "linux", target_os = "freebsd"),
-    any(feature = "wayland", feature = "x11"),
-))]
-pub(crate) mod scap_screen_capture;
-
 use crate::{
     Action, AnyWindowHandle, App, AsyncWindowContext, BackgroundExecutor, Bounds,
     DEFAULT_WINDOW_SIZE, DevicePixels, DispatchEventResult, Font, FontId, FontMetrics, FontRun,
@@ -164,7 +158,6 @@ pub(crate) trait Platform: 'static {
         None
     }
 
-    fn is_screen_capture_supported(&self) -> bool;
     fn screen_capture_sources(
         &self,
     ) -> oneshot::Receiver<Result<Vec<Box<dyn ScreenCaptureSource>>>>;
@@ -253,14 +246,13 @@ pub trait PlatformDisplay: Send + Sync + Debug {
 /// A source of on-screen video content that can be captured.
 pub trait ScreenCaptureSource {
     /// Returns the video resolution of this source.
-    fn resolution(&self) -> Result<Size<DevicePixels>>;
+    fn resolution(&self) -> Result<Size<Pixels>>;
 
     /// Start capture video from this source, invoking the given callback
     /// with each frame.
     fn stream(
         &self,
-        foreground_executor: &ForegroundExecutor,
-        frame_callback: Box<dyn Fn(ScreenCaptureFrame) + Send>,
+        frame_callback: Box<dyn Fn(ScreenCaptureFrame)>,
     ) -> oneshot::Receiver<Result<Box<dyn ScreenCaptureStream>>>;
 }