Keep editor at normal priority on windows.

The multithreaded importer often causes system-wide hangs when importing more than 20 files at a time.
Running the editor at normal priority allows other applications on the system to be responsive during long imports.

(cherry picked from commit ee02a7f785b672304346028bc500949050432fa5)

platform/windows/os_windows.cpp

@@ -1627,8 +1627,11 @@ Error OS_Windows::initialize(const VideoMode &p_desired, int p_video_driver, int
 
 	set_ime_active(false);
 
-	if (!OS::get_singleton()->is_in_low_processor_usage_mode()) {
-		//SetPriorityClass(GetCurrentProcess(), ABOVE_NORMAL_PRIORITY_CLASS);
+	if (!Engine::get_singleton()->is_editor_hint() && !OS::get_singleton()->is_in_low_processor_usage_mode()) {
+		// Increase priority for projects that are not in low-processor mode (typically games)
+		// to reduce the risk of frame stuttering.
+		// This is not done for the editor to prevent importers or resource bakers
+		// from making the system unresponsive.
 		SetPriorityClass(GetCurrentProcess(), ABOVE_NORMAL_PRIORITY_CLASS);
 		DWORD index = 0;
 		HANDLE handle = AvSetMmThreadCharacteristics("Games", &index);