[Macros] Update the name and argument list for the function body macro

that wraps a function or closure body in a new top-level task.

lib/Macros/Sources/SwiftMacros/SyntaxExtensions.swift

@@ -43,4 +43,17 @@ extension ImplicitlyUnwrappedOptionalTypeSyntax {
       trailingTrivia: self.trailingTrivia
     )
   }
-}
+}
+
+extension LabeledExprListSyntax {
+  /// Retrieve the first element with the given label.
+  func first(labeled name: String) -> Element? {
+    return first { element in
+      if let label = element.label, label.text == name {
+        return true
+      }
+
+      return false
+    }
+  }
+}