Add NewBroadcastChannel functor

Sources/ElixxirDAppsSDK/Functors/NewBroadcastChannel.swift

+import Bindings
+import XCTestDynamicOverlay
+
+public struct NewBroadcastChannel {
+  public var run: (Int, ChannelDef) throws -> Channel
+
+  public func callAsFunction(
+    cmixId: Int,
+    channelDef: ChannelDef
+  ) throws -> Channel {
+    try run(cmixId, channelDef)
+  }
+}
+
+extension NewBroadcastChannel {
+  public static let live = NewBroadcastChannel { cmixId, channelDef in
+    var error: NSError?
+    let bindingsChannel = BindingsNewBroadcastChannel(
+      cmixId,
+      try channelDef.encode(),
+      &error
+    )
+    if let error = error {
+      throw error
+    }
+    guard let bindingsChannel = bindingsChannel else {
+      fatalError("BindingsNewBroadcastChannel returned `nil` without providing error")
+    }
+    return .live(bindingsChannel)
+  }
+}
+
+extension NewBroadcastChannel {
+  public static let unimplemented = NewBroadcastChannel(
+    run: XCTUnimplemented("\(Self.self)")
+  )
+}