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/timelinewidget/tool/tool.cpp

@@ -21,8 +21,6 @@
 
 #include "widget/timelinewidget/timelinewidget.h"
 
-#include "node/block/transition/transition.h"
-
 namespace olive
 {
 
@@ -43,20 +41,20 @@ TimelineWidget *TimelineTool::parent()
 	return parent_;
 }
 
-Sequence *TimelineTool::sequence()
+OakEngineSequence *TimelineTool::sequence()
 {
 	return parent_->sequence();
 }
 
-Timeline::MovementMode
-TimelineTool::flip_trim_mode(const Timeline::MovementMode &trim_mode)
+TimelineApp::MovementMode
+TimelineTool::flip_trim_mode(const TimelineApp::MovementMode &trim_mode)
 {
-	if (trim_mode == Timeline::k_trim_in) {
-		return Timeline::k_trim_out;
+	if (trim_mode == TimelineApp::k_trim_in) {
+		return TimelineApp::k_trim_out;
 	}
 
-	if (trim_mode == Timeline::k_trim_out) {
-		return Timeline::k_trim_in;
+	if (trim_mode == TimelineApp::k_trim_out) {
+		return TimelineApp::k_trim_in;
 	}
 
 	return trim_mode;
@@ -82,7 +80,7 @@ Rational TimelineTool::validate_time_movement(Rational movement)
 	bool first_ghost = true;
 
 	foreach (TimelineViewGhostItem *ghost, parent()->get_ghost_items()) {
-		if (ghost->get_mode() != Timeline::k_move) {
+		if (ghost->get_mode() != TimelineApp::k_move) {
 			continue;
 		}
 
@@ -106,7 +104,7 @@ int TimelineTool::validate_track_movement(
 	int movement, const QVector<TimelineViewGhostItem *> &ghosts)
 {
 	foreach (TimelineViewGhostItem *ghost, ghosts) {
-		if (ghost->get_mode() != Timeline::k_move) {
+		if (ghost->get_mode() != TimelineApp::k_move) {
 			continue;
 		}