These reports were embedded in the window manager DNA,
but they were always cleared when reading it from files. It's clearer
to just not store the reports in files at all. I also moved the reports
initialization and freeing to the constructor and destructor of the
runtime class.
This is the only place `ReportList` was embedded in DNA, so
after this we can move that to use C++ features if we want.
Pull Request: https://projects.blender.org/blender/blender/pulls/118329
