style: unify identifier naming per updated conventions

Automated with clang-tidy readability-identifier-naming (config added to
.clang-tidy) plus scripted passes, per the updated rules now documented
in CONTRIBUTING.md:

- types (class/struct/enum/alias/template params): PascalCase
- functions, variables, members: snake_case (incl. rational -> Rational)
- private/protected members: trailing underscore; static member
  variables likewise (instance_, available_themes_)
- constants and enum values: snake_case (kLinear -> k_linear,
  F32P -> f32p); ALL_CAPS reserved for macros
- macros: OAK_ prefix (OLIVE_ADD_TEST/OLIVE_ASSERT/OLIVE_CONFIG ->
  OAK_ADD_TEST/OAK_ASSERT/OAK_CONFIG, GL_PREAMBLE -> OAK_GL_PREAMBLE,
  include guards -> OAK_*)
- file names: all lowercase (Current/Plugin/OliveHost/OliveClip/
  OlivePluginInstance -> current/plugin/olivehost/oliveclip/
  oliveplugininstance)
- getters share the member name sans underscore, setters set_foo()
- Qt and third-party (OpenFX) virtual overrides and framework callbacks
  keep their original names (exempt in .clang-tidy)

Manual follow-ups required where automation could not reach:
- string-based QMetaObject/SIGNAL/SLOT references updated to renamed
  methods (AddTask, CreatedFile, DeleteSpecificFile, moveSelectionUp, ...)
- macro bodies referencing renamed methods (OLIVE_CONFIG,
  NODE_DEFAULT_DESTRUCTOR, MANAGEDDISPLAYWIDGET_*)
- self-shadowing locals renamed where signals/methods became same-named
  (size_changed, worker_count, selected_items, import param, filters)
- third_party OFX member/namespace usages restored (OFX::Host::*,
  _created, _clipPrefsDirty, createInstance, clearPersistentMessage)
- STL protocol aliases restored (const_iterator) with .clang-tidy
  ignore rules; qHash overloads restored

Full build and test suite pass: ctest 4/4, ~1960 gtest cases green.

app/timeline/timelinecoordinate.cpp

@@ -25,18 +25,18 @@ namespace olive
 {
 
 TimelineCoordinate::TimelineCoordinate()
-	: track_(Track::kNone, 0)
+	: track_(Track::k_none, 0)
 {
 }
 
-TimelineCoordinate::TimelineCoordinate(const rational &frame,
+TimelineCoordinate::TimelineCoordinate(const Rational &frame,
 									   const Track::Reference &track)
 	: frame_(frame)
 	, track_(track)
 {
 }
 
-TimelineCoordinate::TimelineCoordinate(const rational &frame,
+TimelineCoordinate::TimelineCoordinate(const Rational &frame,
 									   const Track::Type &track_type,
 									   const int &track_index)
 	: frame_(frame)
@@ -44,22 +44,22 @@ TimelineCoordinate::TimelineCoordinate(const rational &frame,
 {
 }
 
-const rational &TimelineCoordinate::GetFrame() const
+const Rational &TimelineCoordinate::get_frame() const
 {
 	return frame_;
 }
 
-const Track::Reference &TimelineCoordinate::GetTrack() const
+const Track::Reference &TimelineCoordinate::get_track() const
 {
 	return track_;
 }
 
-void TimelineCoordinate::SetFrame(const rational &frame)
+void TimelineCoordinate::set_frame(const Rational &frame)
 {
 	frame_ = frame;
 }
 
-void TimelineCoordinate::SetTrack(const Track::Reference &track)
+void TimelineCoordinate::set_track(const Track::Reference &track)
 {
 	track_ = track;
 }