SplitContainer refactor (#4261)

* Remove unused include util/Helpers.hpp

* SplitContainer::setTag fix parameter naming

* autofy/constify where possible

* More const auto ptr magicifying

* Make SplitNode::Type an enum class

* Move QuickSwitcherPopup includes from header to source file

* Remove unused DropRegion code

* use empty() instead of size() == 0

* Add curly braces everywhere

* Remove useless reinterpret_cast

It was casting Node* to Node*

* Clarify that the connect is QObject::connect

* SplitContainer::setSelected fix parameter naming

* Rename function variables to remove unneccesary underscore

Also move addSpacing parameter out of the layout function

* emplace_back where possible

* Name parameters

* Remove ineffective const from return type

* Make node getters const

* Flatten Node::releaseSplit

* Rename in-function variable to match code style

* [ACTUAL CODE CHANGE/MOVE] Move clamp logic to its own function

* name params

* applyFromDescriptorRecursively: rename node param to baseNode

* [ACTUAL CODE CHANGE/MOVE] Remove the many overloads for append/insertSplit

This utilizes the C++20 designed initializers aggregate initialization feature

* Remove unused includes

* [ACTUAL CODE CHANGE] Clean up dragging logic

There's no need to keep a pointer around to which split is being
dragged, it's already stored in the QDropEvent source()

* UNRELATED .clang-tidy: Only suggest UPPER_CASE for constant global variables

* Remove unused SplitContainer::getSplitCount function

* Use std::max in Node's clamp function

* Remove test code

* DraggedSplit.hpp: remove unused include

* Split `setDraggingSplit` into two functions, `startDraggingSplit` and `stopDraggingSplit`

src/singletons/WindowManager.cpp

@@ -555,7 +555,7 @@ void WindowManager::encodeNodeRecursively(SplitNode *node, QJsonObject &obj)
 {
     switch (node->getType())
     {
-        case SplitNode::_Split: {
+        case SplitNode::Type::Split: {
             obj.insert("type", "split");
             obj.insert("moderationMode", node->getSplit()->getModerationMode());
 
@@ -569,11 +569,12 @@ void WindowManager::encodeNodeRecursively(SplitNode *node, QJsonObject &obj)
             obj.insert("filters", filters);
         }
         break;
-        case SplitNode::HorizontalContainer:
-        case SplitNode::VerticalContainer: {
-            obj.insert("type", node->getType() == SplitNode::HorizontalContainer
-                                   ? "horizontal"
-                                   : "vertical");
+        case SplitNode::Type::HorizontalContainer:
+        case SplitNode::Type::VerticalContainer: {
+            obj.insert("type",
+                       node->getType() == SplitNode::Type::HorizontalContainer
+                           ? "horizontal"
+                           : "vertical");
 
             QJsonArray itemsArr;
             for (const std::unique_ptr<SplitNode> &n : node->getChildren())