Simplify livekit config so that cargo check Just Works (#21661)

Supersedes https://github.com/zed-industries/zed/pull/21653

This enables us to use `cargo test -p workspace` on macOS and Linux.

Note that the line diffs in `shared_screen.rs` are spurious, I just
re-ordered the `macos` and `cross-platform` modules to match the order
in the call crate.

Release Notes:

- N/A

crates/call/Cargo.toml

@@ -21,8 +21,6 @@ test-support = [
     "project/test-support",
     "util/test-support"
 ]
-livekit-macos = ["livekit_client_macos"]
-livekit-cross-platform = ["livekit_client"]
 
 [dependencies]
 anyhow.workspace = true
@@ -42,8 +40,12 @@ serde.workspace = true
 serde_derive.workspace = true
 settings.workspace = true
 util.workspace = true
-livekit_client_macos = { workspace = true, optional = true }
-livekit_client = { workspace = true, optional = true }
+
+[target.'cfg(target_os = "macos")'.dependencies]
+livekit_client_macos = { workspace = true }
+
+[target.'cfg(not(target_os = "macos"))'.dependencies]
+livekit_client = { workspace = true }
 
 [dev-dependencies]
 client = { workspace = true, features = ["test-support"] }

crates/call/src/call.rs

@@ -1,41 +1,13 @@
 pub mod call_settings;
 
-#[cfg(any(
-    all(target_os = "macos", feature = "livekit-macos"),
-    all(
-        not(target_os = "macos"),
-        feature = "livekit-macos",
-        not(feature = "livekit-cross-platform")
-    )
-))]
+#[cfg(target_os = "macos")]
 mod macos;
 
-#[cfg(any(
-    all(target_os = "macos", feature = "livekit-macos"),
-    all(
-        not(target_os = "macos"),
-        feature = "livekit-macos",
-        not(feature = "livekit-cross-platform")
-    )
-))]
+#[cfg(target_os = "macos")]
 pub use macos::*;
 
-#[cfg(any(
-    all(
-        target_os = "macos",
-        feature = "livekit-cross-platform",
-        not(feature = "livekit-macos"),
-    ),
-    all(not(target_os = "macos"), feature = "livekit-cross-platform"),
-))]
+#[cfg(not(target_os = "macos"))]
 mod cross_platform;
 
-#[cfg(any(
-    all(
-        target_os = "macos",
-        feature = "livekit-cross-platform",
-        not(feature = "livekit-macos"),
-    ),
-    all(not(target_os = "macos"), feature = "livekit-cross-platform"),
-))]
+#[cfg(not(target_os = "macos"))]
 pub use cross_platform::*;