Use a separate executor/thread for ClientSync

Summary: Sometimes ClientSync never gets created because the relevant task, which is scheduled on an executor, is never called. We do not know the root cause, but we (Kay, Michael, JP, and I) attempt to minimize the severity of the issue by creating a separate executor/thread for ClientSync on every new TW cast session.

Differential Revision: D51184111

fbshipit-source-id: 7fa7265f928671d95c1791eb111707584fb16efe

cxx/fbjni/JThread.h

@@ -65,6 +65,12 @@ class JThread : public JavaClass<JThread> {
     static const auto method = getClass()->getMethod<void(int)>("setPriority");
     method(self(), priority);
   }
+
+  void setName(const std::string& name) {
+    static const auto method =
+        getClass()->getMethod<void(alias_ref<JString>)>("setName");
+    method(self(), make_jstring(std::move(name)));
+  }
 };
 
 } // namespace jni