[Concurrency] Fix task status and private storage sizes.

ActiveTaskStatusSize is 2 words, not 4, on most targets.

PrivateStorageSize is measured in bytes, not words, so the Storage field needs to be a char[].

Author: mikeash

include/swift/ABI/Task.h

@@ -301,15 +301,15 @@ class AsyncTask : public Job {
 #if SWIFT_CONCURRENCY_ENABLE_PRIORITY_ESCALATION && SWIFT_POINTER_IS_4_BYTES
     static constexpr size_t ActiveTaskStatusSize = 4 * sizeof(void *);
 #else
-    static constexpr size_t ActiveTaskStatusSize = 4 * sizeof(void *);
+    static constexpr size_t ActiveTaskStatusSize = 2 * sizeof(void *);
 #endif
 
     // Private storage is currently 6 pointers, 16 bytes of non-pointer data,
     // the ActiveTaskStatus, and a RecursiveMutex.
     static constexpr size_t PrivateStorageSize =
         6 * sizeof(void *) + 16 + ActiveTaskStatusSize + sizeof(RecursiveMutex);
 
-    void *Storage[PrivateStorageSize];
+    char Storage[PrivateStorageSize];
 
     /// Initialize this storage during the creation of a task.
     void initialize(JobPriority basePri);