UI: Add advanced scene collection importer

This replaces the previous Open File dialog for importing collections
with a window for importing many collections at once, based on the remux
window, along with support for importing from OBS Classic, XSplit
Broadcaster and from Streamlabs' fork. This also translates sources
between OSes that Studio supports.

UI/window-basic-settings.cpp

@@ -354,6 +354,7 @@ OBSBasicSettings::OBSBasicSettings(QWidget *parent)
 	HookWidget(ui->overflowHide,         CHECK_CHANGED,  GENERAL_CHANGED);
 	HookWidget(ui->overflowAlwaysVisible,CHECK_CHANGED,  GENERAL_CHANGED);
 	HookWidget(ui->overflowSelectionHide,CHECK_CHANGED,  GENERAL_CHANGED);
+	HookWidget(ui->automaticSearch,      CHECK_CHANGED,  GENERAL_CHANGED);
 	HookWidget(ui->doubleClickSwitch,    CHECK_CHANGED,  GENERAL_CHANGED);
 	HookWidget(ui->studioPortraitLayout, CHECK_CHANGED,  GENERAL_CHANGED);
 	HookWidget(ui->prevProgLabelToggle,  CHECK_CHANGED,  GENERAL_CHANGED);
@@ -1200,6 +1201,10 @@ void OBSBasicSettings::LoadGeneralSettings()
 		GetGlobalConfig(), "BasicWindow", "OverflowSelectionHidden");
 	ui->overflowSelectionHide->setChecked(overflowSelectionHide);
 
+	bool automaticSearch = config_get_bool(GetGlobalConfig(), "General",
+					       "AutomaticCollectionSearch");
+	ui->automaticSearch->setChecked(automaticSearch);
+
 	bool doubleClickSwitch = config_get_bool(
 		GetGlobalConfig(), "BasicWindow", "TransitionOnDoubleClick");
 	ui->doubleClickSwitch->setChecked(doubleClickSwitch);
@@ -2857,6 +2862,10 @@ void OBSBasicSettings::SaveGeneralSettings()
 		config_set_bool(GetGlobalConfig(), "BasicWindow",
 				"TransitionOnDoubleClick",
 				ui->doubleClickSwitch->isChecked());
+	if (WidgetChanged(ui->automaticSearch))
+		config_set_bool(GetGlobalConfig(), "General",
+				"AutomaticCollectionSearch",
+				ui->automaticSearch->isChecked());
 
 	config_set_bool(GetGlobalConfig(), "BasicWindow",
 			"WarnBeforeStartingStream",