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/livekit_client_macos/LiveKitBridge/Package.swift

@@ -0,0 +1,27 @@
+// swift-tools-version: 5.5
+
+import PackageDescription
+
+let package = Package(
+    name: "LiveKitBridge",
+    platforms: [
+        .macOS(.v10_15)
+    ],
+    products: [
+        // Products define the executables and libraries a package produces, and make them visible to other packages.
+        .library(
+            name: "LiveKitBridge",
+            type: .static,
+            targets: ["LiveKitBridge"]),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/livekit/client-sdk-swift.git", .exact("1.0.12")),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages this package depends on.
+        .target(
+            name: "LiveKitBridge",
+            dependencies: [.product(name: "LiveKit", package: "client-sdk-swift")]),
+    ]
+)