Create more test cases for async timer functions set_timeout and set_interval

[adityarao2005]

Create test cases for set_timeout and set_interval which exist in webcraft/async/runtime.hpp

Something simple like the following:

      // set timeout test
     runtime_context ctx;
     
     event_signal signal;
     
      auto f = async {
     
        set_timeout([signal]() { signal.set(); }, 100ms);
     
        co_await sleep_for(100ms);
     
        EXPECT_TRUE(signal.is_set());
      };
     
      sync_wait(f());

Maybe an atomic counter for the set_interval?