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/dialog/about/scrollinglabel.cpp

@@ -28,23 +28,23 @@
 namespace olive
 {
 
-const int ScrollingLabel::kMinLineHeight = 10;
+const int ScrollingLabel::k_min_line_height = 10;
 
 ScrollingLabel::ScrollingLabel(QWidget *parent)
 	: QWidget(parent)
 	, animate_(0)
 {
 	timer_.setInterval(50);
-	connect(&timer_, &QTimer::timeout, this, &ScrollingLabel::AnimationUpdate);
+	connect(&timer_, &QTimer::timeout, this, &ScrollingLabel::animation_update);
 }
 
 ScrollingLabel::ScrollingLabel(const QStringList &text, QWidget *parent)
 	: ScrollingLabel(parent)
 {
-	SetText(text);
+	set_text(text);
 }
 
-void ScrollingLabel::SetText(const QStringList &text)
+void ScrollingLabel::set_text(const QStringList &text)
 {
 	text_ = text;
 
@@ -53,10 +53,10 @@ void ScrollingLabel::SetText(const QStringList &text)
 
 	int width = 0;
 	foreach (const QString &s, text_) {
-		width = qMax(width, QtUtils::QFontMetricsWidth(fm, s));
+		width = qMax(width, QtUtils::q_font_metrics_width(fm, s));
 	}
 
-	setMinimumSize(width, text_height_ * kMinLineHeight);
+	setMinimumSize(width, text_height_ * k_min_line_height);
 }
 
 void ScrollingLabel::paintEvent(QPaintEvent *e)
@@ -82,15 +82,15 @@ void ScrollingLabel::paintEvent(QPaintEvent *e)
 
 			const QString &s = text_.at(i);
 
-			int width = QtUtils::QFontMetricsWidth(fm, s);
+			int width = QtUtils::q_font_metrics_width(fm, s);
 			p.drawText(half_width / 2 - width / 2, text_y, s);
 		}
 
 		for (int y = 0; y < text_height_; y++) {
 			double mul = double(y) / double(text_height_);
 
-			SetOpacityOfScanLine(map.scanLine(y), map.width(), 4, mul);
-			SetOpacityOfScanLine(map.scanLine(map.height() - 1 - y),
+			set_opacity_of_scan_line(map.scanLine(y), map.width(), 4, mul);
+			set_opacity_of_scan_line(map.scanLine(map.height() - 1 - y),
 								 map.width(), 4, mul);
 		}
 	}
@@ -99,7 +99,7 @@ void ScrollingLabel::paintEvent(QPaintEvent *e)
 	wp.drawImage(0, 0, map);
 }
 
-void ScrollingLabel::SetOpacityOfScanLine(uchar *scan_line, int width,
+void ScrollingLabel::set_opacity_of_scan_line(uchar *scan_line, int width,
 										  int channels, double mul)
 {
 	for (int x = 0; x < width; x++) {
@@ -111,7 +111,7 @@ void ScrollingLabel::SetOpacityOfScanLine(uchar *scan_line, int width,
 	}
 }
 
-void ScrollingLabel::AnimationUpdate()
+void ScrollingLabel::animation_update()
 {
 	animate_++;