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/audio/audiosynchronizer.cpp

@@ -23,9 +23,9 @@
 namespace olive
 {
 
-AudioSynchronizer::Placement AudioSynchronizer::PlaceBySourceTime(
+AudioSynchronizer::Placement AudioSynchronizer::place_by_source_time(
 	const SourceClip &reference, const SourceClip &candidate,
-	const core::rational &reference_timeline_in)
+	const core::Rational &reference_timeline_in)
 {
 	Placement placement;
 	if (!reference.has_source_start_time || !candidate.has_source_start_time ||
@@ -34,9 +34,9 @@ AudioSynchronizer::Placement AudioSynchronizer::PlaceBySourceTime(
 		return placement;
 	}
 
-	const core::rational reference_head_source =
+	const core::Rational reference_head_source =
 		reference.source_start_time + reference.media_in;
-	const core::rational candidate_head_source =
+	const core::Rational candidate_head_source =
 		candidate.source_start_time + candidate.media_in;
 
 	placement.timeline_in =
@@ -45,8 +45,8 @@ AudioSynchronizer::Placement AudioSynchronizer::PlaceBySourceTime(
 	return placement;
 }
 
-AudioSynchronizer::Placement AudioSynchronizer::PlaceByWaveformOffset(
-	const core::rational &reference_timeline_in,
+AudioSynchronizer::Placement AudioSynchronizer::place_by_waveform_offset(
+	const core::Rational &reference_timeline_in,
 	int64_t candidate_offset_samples, int sample_rate)
 {
 	Placement placement;
@@ -55,7 +55,7 @@ AudioSynchronizer::Placement AudioSynchronizer::PlaceByWaveformOffset(
 	}
 
 	placement.timeline_in = reference_timeline_in +
-							core::rational::fromDouble(
+							core::Rational::from_double(
 								static_cast<double>(candidate_offset_samples) /
 								static_cast<double>(sample_rate));
 	placement.valid = !placement.timeline_in.isNaN();