Don't block UI while executing long runnig actions

The previous approach had the problem of losing any action internal
state changes in the created copy.

Revert "Fix temp var values of actions not being accessible"
This reverts commit df42538319.
Revert "Don't block UI while running actions"
This reverts commit a01d26e25d.

lib/utils/sync-helpers.cpp

@@ -66,4 +66,15 @@ void Lockable::WithLock(const std::function<void()> &func)
 	func();
 }
 
+SuspendLock::SuspendLock(Lockable &lockable)
+	: _mtx(static_cast<std::mutex &>(lockable._mtx))
+{
+	_mtx.unlock();
+}
+
+SuspendLock::~SuspendLock()
+{
+	_mtx.lock();
+}
+
 } // namespace advss