trashsizecache: Fix look up of directory size cache
For performance reasons, directory sizes are cached in a "directorysizes" file. The file name is written using percent encoding but read back without, which means any directory with a space or special character will effectively not be cached (it won't find it again), significantly impcating performance when trashing files.
I currently have 1.6 GiB in Trash (14 folders on root level and 629 files). Before, every call to TrashSizeCache::calculateSize took 100 (!) ms. Now it takes 2 ms. It’s still not ideal that we do this for every single file trashed but at least it’s significantly faster now, assuming you have folders with special characters and spaces in trash.