R8: finish app/ pure C ABI migration (P3-P9) and make OTIO required

- app/ no longer includes engine C++ headers nor holds engine C++ types:
  engine access goes through the oakengine C ABI plus C++ wrappers
  (oakutil/oaknode.h, oakutil/oakvideo.h) and app-local mirror types
  (tooltypes, trackreferencehandle, timelinecommonapp, keyframetypes,
  subtitleapp, serializedlayoutinfoapp, nodevaluehandle, sliderdisplaytypeapp)
- engine: new C ABI functions for block/track/clip/transition navigation
  and predicates, links, caches, waveform/playback, disk folder,
  sequence_track_list, node_free, footage_is_valid, block_get_track,
  get_brush; loadotio/saveotio ported to the current engine API
- OTIO is now a required dependency: CI and CD build it on every
  platform, FindOpenTimelineIO fixed for OTIO 0.16/0.19 (the old deps
  include requirement silently disabled OTIO everywhere), runtime
  libraries are bundled into packages and copied next to macOS binaries
  (oak_copy_otio_runtime)
- fix ProjectViewModel drag&drop mime read/write size mismatch (segfault)
- unify color label naming (k_olive -> "Oak") in the app-side mirror
- docs: OTIO required, FFmpeg minimum corrected to 6.0 (en/zh)
- gtest suite: 1925 passed, 0 failed

app/widget/nodeview/nodeviewedge.h

@@ -26,7 +26,7 @@
 #include <QPalette>
 
 #include "nodeviewcommon.h"
-#include "node/node.h"
+#include "oakutil/oaknode.h"
 
 namespace olive
 {
@@ -40,19 +40,20 @@ class NodeViewItem;
  */
 class NodeViewEdge : public QGraphicsPathItem {
 public:
-	NodeViewEdge(Node *output, const NodeInput &input, NodeViewItem *from_item,
+	NodeViewEdge(oak::Node output, const oak::Input &input,
+				 NodeViewItem *from_item,
 				 NodeViewItem *to_item, QGraphicsItem *parent = nullptr);
 
 	NodeViewEdge(QGraphicsItem *parent = nullptr);
 
 	virtual ~NodeViewEdge() override;
 
-	Node *output() const
+	oak::Node output() const
 	{
 		return output_;
 	}
 
-	const NodeInput &input() const
+	const oak::Input &input() const
 	{
 		return input_;
 	}
@@ -122,9 +123,9 @@ private:
 
 	void update_curve();
 
-	Node *output_;
+	oak::Node output_;
 
-	NodeInput input_;
+	oak::Input input_;
 
 	int element_;