wayland: Implement activate() API and use portals to open URLs and paths (#13336)

This PR consists of two main changes:
1. The first commit changes the `open` crate for opening URLs/paths for
the `OpenURI` desktop portal. This fixes the activation token not being
passed to programs (at least on KDE).
2. The second commit implements the window `activate()` API on Wayland.
This allows KWin and Mutter to show a visual indicator when the window
is requesting attention. (see
https://github.com/zed-industries/zed/issues/12557)

![image](https://github.com/zed-industries/zed/assets/71973804/ce148f8e-28fd-4249-8f8d-3a5828ed6f83)


Release Notes:

- N/A

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

@@ -81,6 +81,8 @@ impl LinuxClient for HeadlessClient {
 
     fn open_uri(&self, _uri: &str) {}
 
+    fn reveal_path(&self, _path: std::path::PathBuf) {}
+
     fn write_to_primary(&self, _item: crate::ClipboardItem) {}
 
     fn write_to_clipboard(&self, _item: crate::ClipboardItem) {}