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/sequence/sequence.cpp

@@ -36,11 +36,12 @@
 #include "oakengine/node.h"
 #include "oakengine/timeline.h"
 #include "oakengine/videoparams.h"
+#include "oakutil/oaknode.h"
 
 namespace olive
 {
 
-SequenceDialog::SequenceDialog(Sequence *s, Type t, QWidget *parent)
+SequenceDialog::SequenceDialog(OakEngineNode *s, Type t, QWidget *parent)
 	: QDialog(parent)
 	, sequence_(s)
 	, make_undoable_(true)
@@ -89,11 +90,12 @@ SequenceDialog::SequenceDialog(Sequence *s, Type t, QWidget *parent)
 		setWindowTitle(tr("New Sequence"));
 		break;
 	case k_existing:
-		setWindowTitle(tr("Editing \"%1\"").arg(sequence_->get_label()));
+		setWindowTitle(
+			tr("Editing \"%1\"").arg(oak::Node(sequence_).get_label()));
 		break;
 	}
 
-	name_field_->setText(sequence_->get_label());
+	name_field_->setText(oak::Node(sequence_).get_label());
 }
 
 void SequenceDialog::set_undoable(bool u)

app/dialog/sequence/sequence.h

@@ -26,10 +26,11 @@
 #include <QDialog>
 #include <QSpinBox>
 
-#include "node/project/sequence/sequence.h"
 #include "sequencedialogparametertab.h"
 #include "sequencedialogpresettab.h"
 
+struct OakEngineNode;
+
 namespace olive
 {
 
@@ -67,7 +68,7 @@ public:
    * @param parent
    * QWidget parent
    */
-	SequenceDialog(Sequence *s, Type t = k_existing, QWidget *parent = nullptr);
+	SequenceDialog(OakEngineNode *s, Type t = k_existing, QWidget *parent = nullptr);
 
 	/**
    * @brief Set whether the parameter changes should be made into an undo command or not
@@ -90,7 +91,7 @@ public slots:
 	virtual void accept() override;
 
 private:
-	Sequence *sequence_;
+	OakEngineNode *sequence_;
 
 	SequenceDialogPresetTab *preset_tab_;
 

app/dialog/sequence/sequencedialogparametertab.cpp

@@ -29,7 +29,7 @@
 namespace olive
 {
 
-SequenceDialogParameterTab::SequenceDialogParameterTab(Sequence *sequence,
+SequenceDialogParameterTab::SequenceDialogParameterTab(OakEngineNode *sequence,
 													   QWidget *parent)
 	: QWidget(parent)
 {

app/dialog/sequence/sequencedialogparametertab.h

@@ -24,18 +24,20 @@
 #include <QList>
 #include <QSpinBox>
 
-#include "node/project/sequence/sequence.h"
 #include "sequencepreset.h"
 #include "widget/slider/integerslider.h"
 #include "widget/standardcombos/standardcombos.h"
 
+struct OakEngineNode;
+
 namespace olive
 {
 
 class SequenceDialogParameterTab : public QWidget {
 	Q_OBJECT
 public:
-	SequenceDialogParameterTab(Sequence *sequence, QWidget *parent = nullptr);
+	SequenceDialogParameterTab(OakEngineNode *sequence,
+							   QWidget *parent = nullptr);
 
 	int get_selected_video_width() const
 	{

app/dialog/sequence/sequencepreset.h

@@ -27,11 +27,14 @@
 
 #include "oakutil/xmlutils.h"
 #include "dialog/sequence/presetmanager.h"
-#include "render/videoparams.h"
 
 namespace olive
 {
 
+// Same namespace bridge the engine's render/videoparams.h used to provide
+// (unqualified Rational/PixelFormat inside namespace olive).
+using namespace core;
+
 class SequencePreset : public Preset {
 public:
 	SequencePreset() = default;