[Concurrency] Adopt stable keyword consuming instead of __owned

add test for warnings emitted when missing consuming attribute

use -emit-sil in mock SDK tests for better coverage

stdlib/public/Distributed/DistributedDefaultExecutor.swift

@@ -24,7 +24,7 @@ internal final class DistributedRemoteActorReferenceExecutor: SerialExecutor {
   internal init() {}
 
   @inlinable
-  public func enqueue(_ job: __owned ExecutorJob) {
+  public func enqueue(_ job: consuming ExecutorJob) {
     let jobDescription = job.description
     fatalError("Attempted to enqueue ExecutorJob (\(jobDescription)) on executor of remote distributed actor reference!")
   }