[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/OptionSetMacro.swift

@@ -47,19 +47,6 @@ private let optionsEnumNameArgumentLabel = "optionsName"
 /// eventually be overridable.
 private let defaultOptionsEnumName = "Options"
 
-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
-    }
-  }
-}
-
 public struct OptionSetMacro {
   /// Decodes the arguments to the macro expansion.
   ///