Abstract away InstanceCopyPrefs' internals through new getSelectedFiltersAsRegex() function

+ fix typo in comment
+ remove unused import
+ add [[nodiscard]] to methods

Signed-off-by: Marcelo Hernandez <marcelohdez.inq@gmail.com>

launcher/InstanceCopyPrefs.h

@@ -5,6 +5,8 @@
 #ifndef LAUNCHER_INSTANCECOPYPREFS_H
 #define LAUNCHER_INSTANCECOPYPREFS_H
 
+#include <QStringList>
+
 struct InstanceCopyPrefs {
     bool copySaves = true;
     bool keepPlaytime = true;
@@ -14,7 +16,8 @@ struct InstanceCopyPrefs {
     bool copyServers = true;
     bool copyMods = true;
 
-    bool allTrue() const;
+    [[nodiscard]] bool allTrue() const;
+    [[nodiscard]] QString getSelectedFiltersAsRegex() const;
 };
 
 #endif  // LAUNCHER_INSTANCECOPYPREFS_H