Use LiveKit's Rust SDK on Linux while continue using Swift SDK on Mac (#21550)

Similar to #20826 but keeps the Swift implementation. There were quite a
few changes in the `call` crate, and so that code now has two variants.

Closes #13714

Release Notes:

- Added preliminary Linux support for voice chat and viewing
screenshares.

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>

crates/zed/Cargo.toml

@@ -126,6 +126,12 @@ welcome.workspace = true
 workspace.workspace = true
 zed_actions.workspace = true
 
+[target.'cfg(target_os = "macos")'.dependencies]
+workspace = { workspace = true, features = ["livekit-macos"] }
+
+[target.'cfg(not(target_os = "macos"))'.dependencies]
+workspace = { workspace = true, features = ["livekit-cross-platform"] }
+
 [target.'cfg(target_os = "windows")'.dependencies]
 windows.workspace = true