ControllerInterface: devices population is now async so implement devices sorting priority

This helps us keeping the most important devices (e.g. Mouse and Keyboard) on the top
of the list of devices (they still are on all OSes supported by dolphin
and to make hotplug devices like DSU appear at the bottom.

Source/Core/InputCommon/ControllerInterface/ControllerInterface.cpp

@@ -319,6 +319,19 @@ bool ControllerInterface::AddDevice(std::shared_ptr<ciface::Core::Device> device
 
     NOTICE_LOG_FMT(CONTROLLERINTERFACE, "Added device: {}", device->GetQualifiedName());
     m_devices.emplace_back(std::move(device));
+
+    // We can't (and don't want) to control the order in which devices are added, but we
+    // need their order to be consistent, and we need the same one to always be the first, where
+    // present (the keyboard and mouse device usually). This is because when defaulting a
+    // controller profile, it will automatically select the first device in the list as its default.
+    std::stable_sort(m_devices.begin(), m_devices.end(),
+                     [](const std::shared_ptr<ciface::Core::Device>& a,
+                        const std::shared_ptr<ciface::Core::Device>& b) {
+                       // It would be nice to sort devices by Source then Name then ID but it's
+                       // better to leave them sorted by the add order, which also avoids breaking
+                       // the order on other platforms that are less tested.
+                       return a->GetSortPriority() > b->GetSortPriority();
+                     });
   }
 
   if (!m_populating_devices_counter)