[needs-docs] Remove some rendering options from settings dialog

Removes

- Use render caching option
- Render layers in parallel option

These two options are enabled by default and have been for many
many years without issues. Now users are more likely to run
into issues by disabling these options, and there's really
no good reason why they should do so.

Also remove the "show map canvas refresh in log" option, which
is a developer focused option which doesn't need to be exposed
widely.

(all options remain available through the advanced settings
panel for users who REALLY REALLY want to change them)

src/app/options/qgsoptions.cpp

@@ -541,9 +541,6 @@ QgsOptions::QgsOptions( QWidget *parent, Qt::WindowFlags fl, const QList<QgsOpti
 
   mCheckMonitorDirectories->setChecked( mSettings->value( QStringLiteral( "/qgis/monitorDirectoriesInBrowser" ), true ).toBool() );
 
-  // log rendering events, for userspace debugging
-  mLogCanvasRefreshChkBx->setChecked( QgsMapRendererJob::settingsLogCanvasRefreshEvent.value() );
-
   //set the default projection behavior radio buttons
   const QgsOptions::UnknownLayerCrsBehavior mode = QgsSettings().enumValue( QStringLiteral( "/projections/unknownCrsBehavior" ), QgsOptions::UnknownLayerCrsBehavior::NoAction, QgsSettings::App );
   switch ( mode )
@@ -718,8 +715,6 @@ QgsOptions::QgsOptions( QWidget *parent, Qt::WindowFlags fl, const QList<QgsOpti
   //set the state of the checkboxes
   //Changed to default to true as of QGIS 1.7
   chkAntiAliasing->setChecked( mSettings->value( QStringLiteral( "/qgis/enable_anti_aliasing" ), true ).toBool() );
-  chkUseRenderCaching->setChecked( mSettings->value( QStringLiteral( "/qgis/enable_render_caching" ), true ).toBool() );
-  chkParallelRendering->setChecked( mSettings->value( QStringLiteral( "/qgis/parallel_rendering" ), true ).toBool() );
   spinMapUpdateInterval->setValue( mSettings->value( QStringLiteral( "/qgis/map_update_interval" ), 250 ).toInt() );
   spinMapUpdateInterval->setClearValue( 250 );
   chkMaxThreads->setChecked( QgsApplication::maxThreads() != -1 );
@@ -1708,8 +1703,6 @@ void QgsOptions::saveOptions()
 
   mSettings->setValue( QStringLiteral( "/qgis/new_layers_visible" ), chkAddedVisibility->isChecked() );
   mSettings->setValue( QStringLiteral( "/qgis/enable_anti_aliasing" ), chkAntiAliasing->isChecked() );
-  mSettings->setValue( QStringLiteral( "/qgis/enable_render_caching" ), chkUseRenderCaching->isChecked() );
-  mSettings->setValue( QStringLiteral( "/qgis/parallel_rendering" ), chkParallelRendering->isChecked() );
   int maxThreads = chkMaxThreads->isChecked() ? spinMaxThreads->value() : -1;
   QgsApplication::setMaxThreads( maxThreads );
   mSettings->setValue( QStringLiteral( "/qgis/max_threads" ), maxThreads );
@@ -1795,9 +1788,6 @@ void QgsOptions::saveOptions()
   mSettings->setValue( QStringLiteral( "/Raster/cumulativeCutLower" ), mRasterCumulativeCutLowerDoubleSpinBox->value() / 100.0 );
   mSettings->setValue( QStringLiteral( "/Raster/cumulativeCutUpper" ), mRasterCumulativeCutUpperDoubleSpinBox->value() / 100.0 );
 
-  // log rendering events, for userspace debugging
-  QgsMapRendererJob::settingsLogCanvasRefreshEvent.setValue( mLogCanvasRefreshChkBx->isChecked() );
-
   //check behavior so default projection when new layer is added with no
   //projection defined...
   if ( radPromptForProjection->isChecked() )