Fix spinwaiting in LockFreeReaderHashtable (dotnet#55082)

Task.Delay(1).Wait() is variant of sync-over-async anti-patern. It does not work well with threadpool used to run parallel AOT compilation. It can lead to too many threadpool threads getting created and progress slowing down to crawl, at least temporarily.

src/coreclr/tools/Common/TypeSystem/Common/Utilities/LockFreeReaderHashtable.cs

@@ -245,20 +245,14 @@ private TValue WaitForSentinelInHashtableToDisappear(TValue[] hashtable, int tab
             if (sentinel == null)
                 return null;
 
-            TValue value = Volatile.Read(ref hashtable[tableIndex]);
+            var sw = new SpinWait();
             while (true)
             {
-                for (int i = 0; (i < 10000) && value == sentinel; i++)
-                {
-                    value = Volatile.Read(ref hashtable[tableIndex]);
-                }
+                TValue value = Volatile.Read(ref hashtable[tableIndex]);
                 if (value != sentinel)
-                    break;
-
-                Task.Delay(1).Wait();
+                    return value;
+                sw.SpinOnce();
             }
-
-            return value;
         }
 
         /// <summary>