Merge forward and tablet input filters

The primary purpose of the tablet input filter is to forward tablet
input to the clients. On the other hand, the purpose of the forward
input filter is to send input to the clients too.

In order to clean things up, this change merges the two.

src/input.cpp

@@ -2056,18 +2056,6 @@ public:
         seat->cancelPointerHoldGesture();
         return true;
     }
-};
-
-/**
- * Handles input coming from a tablet device (e.g. wacom) often with a pen
- */
-class TabletInputFilter : public QObject, public InputEventFilter
-{
-public:
-    TabletInputFilter()
-        : InputEventFilter(InputFilterOrder::Tablet)
-    {
-    }
 
     bool tabletToolEvent(TabletEvent *event) override
     {
@@ -2871,9 +2859,6 @@ void InputRedirection::setupInputFilters()
 
     m_forwardFilter = std::make_unique<ForwardInputFilter>();
     installInputEventFilter(m_forwardFilter.get());
-
-    m_tabletFilter = std::make_unique<TabletInputFilter>();
-    installInputEventFilter(m_tabletFilter.get());
 }
 
 void InputRedirection::handleInputConfigChanged(const KConfigGroup &group)

src/input.h

@@ -340,7 +340,6 @@ private:
     std::unique_ptr<InputEventFilter> m_internalWindowFilter;
     std::unique_ptr<InputEventFilter> m_inputKeyboardFilter;
     std::unique_ptr<InputEventFilter> m_forwardFilter;
-    std::unique_ptr<InputEventFilter> m_tabletFilter;
 
     std::unique_ptr<InputEventSpy> m_hideCursorSpy;
     std::unique_ptr<InputEventSpy> m_userActivitySpy;
@@ -385,7 +384,6 @@ enum Order {
     InternalWindow,
     InputMethod,
     Forward,
-    Tablet
 };
 }