Merge pull request grpc#14600 from vjpai/sst

Thread name needs to only be alphanumeric+underscore+dash

src/cpp/thread_manager/thread_manager.cc

@@ -32,7 +32,7 @@ ThreadManager::WorkerThread::WorkerThread(ThreadManager* thd_mgr)
  // Make thread creation exclusive with respect to its join happening in
  // ~WorkerThread().
  thd_ = grpc_core::Thread(
- "sync server thread",
+ "grpcpp_sync_server",
  [](void* th) { static_cast<ThreadManager::WorkerThread*>(th)->Run(); },
  this);
  thd_.Start();