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/render/lutlibrary.cpp

@@ -29,7 +29,7 @@
 namespace olive
 {
 
-bool LUTLibrary::IsSupportedExtension(const QString &suffix)
+bool LUTLibrary::is_supported_extension(const QString &suffix)
 {
 	QString s = suffix;
 	if (s.startsWith(QLatin1Char('.'))) {
@@ -40,9 +40,9 @@ bool LUTLibrary::IsSupportedExtension(const QString &suffix)
 	return lower == QStringLiteral("cube") || lower == QStringLiteral("3dl");
 }
 
-QStringList LUTLibrary::GetDirectories()
+QStringList LUTLibrary::get_directories()
 {
-	const QString serialized = OLIVE_CONFIG("LUTLibraryPaths").toString();
+	const QString serialized = OAK_CONFIG("LUTLibraryPaths").toString();
 
 	QStringList dirs = serialized.split(QLatin1Char(';'), Qt::SkipEmptyParts);
 	for (QString &dir : dirs) {
@@ -51,7 +51,7 @@ QStringList LUTLibrary::GetDirectories()
 	return dirs;
 }
 
-void LUTLibrary::SetDirectories(const QStringList &dirs)
+void LUTLibrary::set_directories(const QStringList &dirs)
 {
 	QStringList cleaned;
 	for (const QString &dir : dirs) {
@@ -61,19 +61,19 @@ void LUTLibrary::SetDirectories(const QStringList &dirs)
 		}
 	}
 
-	Config::Current()[QStringLiteral("LUTLibraryPaths")] =
+	Config::current()[QStringLiteral("LUTLibraryPaths")] =
 		cleaned.join(QLatin1Char(';'));
 }
 
-QStringList LUTLibrary::GetLutFiles()
+QStringList LUTLibrary::get_lut_files()
 {
 	QStringList files;
 
-	static const QStringList kFilters = { QStringLiteral("*.cube"),
+	static const QStringList k_filters = { QStringLiteral("*.cube"),
 										  QStringLiteral("*.3dl") };
 
-	for (const QString &dir : GetDirectories()) {
-		QDirIterator it(dir, kFilters, QDir::Files,
+	for (const QString &dir : get_directories()) {
+		QDirIterator it(dir, k_filters, QDir::Files,
 						QDirIterator::Subdirectories);
 		while (it.hasNext()) {
 			files.append(it.next());