perf: Fix more clazy qstring-allocation warnings and pass parameters by reference (#910)

* Fix some more clazy-qstring-allocation warnings

* Fix missing refs on large types in lib_gui

* Fix trivially copyable types being passed by ref in lib_gui

src/lib_gui/qt/element/code/QtCodeFileList.h

@@ -28,7 +28,7 @@ public:
 	void clear();
 	void clearSnippetTitleAndScrollBar();
 
-	QtCodeFile* getFile(const FilePath filePath);
+	QtCodeFile* getFile(const FilePath& filePath);
 
 	void addFile(const CodeFileParams& params);