refactor: Move interval timer into a separate class (#1588)

For #442.

tests/common/util/AsioContextTestFixture.hpp

@@ -26,6 +26,7 @@
 #include <boost/asio/spawn.hpp>
 #include <gmock/gmock.h>
 
+#include <chrono>
 #include <optional>
 #include <thread>
 
@@ -97,6 +98,13 @@ struct SyncAsioContextTest : virtual public NoLoggerFixture {
         ctx.reset();
     }
 
+    void
+    runContextFor(std::chrono::milliseconds duration)
+    {
+        ctx.run_for(duration);
+        ctx.reset();
+    }
+
 protected:
     boost::asio::io_context ctx;
 };