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/speedduration/speeddurationdialog.h

@@ -26,18 +26,16 @@
 #include <QComboBox>
 #include <QDialog>
 
-#include "node/block/gap/gap.h"
+#include "oakengine/timeline.h"
 #include "widget/slider/floatslider.h"
 #include "widget/slider/rationalslider.h"
 
 namespace olive {
 
-class ClipBlock;
-
 class SpeedDurationDialog : public QDialog {
 	Q_OBJECT
 public:
-	explicit SpeedDurationDialog(const QVector<ClipBlock *> &clips,
+	explicit SpeedDurationDialog(const QVector<OakEngineBlock *> &clips,
 								 const Rational &timebase,
 								 QWidget *parent = nullptr);
 
@@ -55,7 +53,7 @@ private:
 									 const Rational &original_length,
 									 const Rational &new_length);
 
-	QVector<ClipBlock *> clips_;
+	QVector<OakEngineBlock *> clips_;
 
 	FloatSlider *speed_slider_;