Some performance optimizations (#5424)

* Some performance optimizations

This is globally removing some memory useless copy

* use a const ref return on std::string Settings::get to prevent data copy on getters which doesn't need to copy it
 * pass some stack created strings to static const as they are not modified anywhere
 * Camera: return nametags per const ref instead of a list pointer, we only need to read it
 * INodeDefManager: getAll should be a result ref writer instead of a return copy
 * INodeDefManager: getAlias should return a const std::string ref
 * Minimap: unroll a Scolor creation in blitMinimapPixersToImageRadar to prvent many variable construct/destruct which are unneeded (we rewrite the content in the loop)
 * CNodeDefManager::updateAliases: prevent a idef getall copy
 * Profiler: constness
 * rollback_interface: create real_name later, and use const ref
 * MapBlockMesh updateFastFaceRow: unroll TileSpec next_tile, which has a cost of 1.8% CPU due to variable allocation/destruction,
 * MapBlockMesh updateFastFaceRow: copy next_tile to tile only if it's a different tilespec
 * MapBlockMesh updateFastFaceRow: use memcpy to copy next_lights to lights to do it in a single cpu operation

1 files changed, 9 insertions, 6 deletions

diff --git a/src/sky.h b/src/sky.h
index f19891773..17d6c5f73 100644
--- a/src/sky.h
+++ b/src/sky.h
@@ -56,18 +56,21 @@ public:
 	void update(float m_time_of_day, float time_brightness,
 			float direct_brightness, bool sunlight_seen, CameraMode cam_mode,
 			float yaw, float pitch);
-	
+
 	float getBrightness(){ return m_brightness; }
 
-	video::SColor getBgColor(){
+	const video::SColor &getBgColor() const
+	{
 		return m_visible ? m_bgcolor : m_fallback_bg_color;
 	}
-	video::SColor getSkyColor(){
+
+	const video::SColor &getSkyColor() const
+	{
 		return m_visible ? m_skycolor : m_fallback_bg_color;
 	}
-	
-	bool getCloudsVisible(){ return m_clouds_visible && m_visible; }
-	video::SColorf getCloudColor(){ return m_cloudcolor_f; }
+
+	bool getCloudsVisible() { return m_clouds_visible && m_visible; }
+	const video::SColorf &getCloudColor() { return m_cloudcolor_f; }
 
 	void setVisible(bool visible){ m_visible = visible; }
 	void setFallbackBgColor(const video::SColor &fallback_bg_color){