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/dialog/keyframeproperties/keyframeproperties.h

@@ -26,7 +26,7 @@
 #include <QDialog>
 #include <QGroupBox>
 
-#include "node/keyframe.h"
+#include "oakutil/oaknode.h"
 #include "widget/slider/floatslider.h"
 #include "widget/slider/rationalslider.h"
 
@@ -36,7 +36,7 @@ namespace olive
 class KeyframePropertiesDialog : public QDialog {
 	Q_OBJECT
 public:
-	KeyframePropertiesDialog(const std::vector<NodeKeyframe *> &keys,
+	KeyframePropertiesDialog(const QVector<oak::Keyframe> &keys,
 							 const Rational &timebase,
 							 QWidget *parent = nullptr);
 
@@ -46,7 +46,7 @@ public slots:
 private:
 	void set_up_bezier_slider(FloatSlider *slider, bool all_same, double value);
 
-	const std::vector<NodeKeyframe *> &keys_;
+	const QVector<oak::Keyframe> &keys_;
 
 	Rational timebase_;