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.cpp

@@ -100,7 +100,7 @@ void QtCodeFileList::clearSnippetTitleAndScrollBar()
 	updateLastSnippetScrollBar(nullptr);
 }
 
-QtCodeFile* QtCodeFileList::getFile(const FilePath filePath)
+QtCodeFile* QtCodeFileList::getFile(const FilePath& filePath)
 {
 	QtCodeFile* file = nullptr;