LibVideo: Rename Status -> State in `PlaybackStatusChangeEvent` class

A bit of a bikeshed, but status sounds more like a result of an action,
and state sounds more accurate to what the `PlaybackManager` does.

The previous and current state fields of the `PlaybackStateChangeEvent`
are now removed, since they were unused (for now).

This is a lead-up to the refactoring of VideoPlaybackManager to make
that diff more legible.

Userland/Applications/VideoPlayer/VideoPlayerWidget.cpp

@@ -234,7 +234,7 @@ void VideoPlayerWidget::event(Core::Event& event)
         set_current_timestamp(m_playback_manager->current_playback_time());
 
         frame_event.accept();
-    } else if (event.type() == Video::EventType::PlaybackStatusChange) {
+    } else if (event.type() == Video::EventType::PlaybackStateChange) {
         update_play_pause_icon();
         event.accept();
     }

Userland/Libraries/LibVideo/PlaybackManager.cpp

@@ -57,7 +57,7 @@ void PlaybackManager::set_playback_status(PlaybackStatus status)
             m_present_timer->stop();
         }
 
-        m_main_loop.post_event(m_event_handler, make<PlaybackStatusChangeEvent>(status, old_status));
+        m_main_loop.post_event(m_event_handler, make<PlaybackStateChangeEvent>());
     }
 }
 

Userland/Libraries/LibVideo/PlaybackManager.h

@@ -165,7 +165,7 @@ private:
 enum EventType : unsigned {
     DecoderErrorOccurred = (('v' << 2) | ('i' << 1) | 'd') << 4,
     VideoFramePresent,
-    PlaybackStatusChange,
+    PlaybackStateChange,
 };
 
 class DecoderErrorEvent : public Core::Event {
@@ -199,20 +199,13 @@ private:
     RefPtr<Gfx::Bitmap> m_frame;
 };
 
-class PlaybackStatusChangeEvent : public Core::Event {
+class PlaybackStateChangeEvent : public Core::Event {
 public:
-    PlaybackStatusChangeEvent() = default;
-    explicit PlaybackStatusChangeEvent(PlaybackStatus status, PlaybackStatus previous_status)
-        : Core::Event(PlaybackStatusChange)
-        , m_status(status)
-        , m_previous_status(previous_status)
+    explicit PlaybackStateChangeEvent()
+        : Core::Event(PlaybackStateChange)
     {
     }
-    virtual ~PlaybackStatusChangeEvent() = default;
-
-private:
-    PlaybackStatus m_status;
-    PlaybackStatus m_previous_status;
+    virtual ~PlaybackStateChangeEvent() = default;
 };
 
 inline StringView playback_status_to_string(PlaybackStatus status)