VizTracer 0.4.1 Release, Bug Fix

Fix flamegraph, it's been not working for a while and I did not realize it.

Fix important command line bugs, where "__name__" is not __main__. Also not even the script run exit() in their code, they will have trace.

Added secret feature fork_save, has not documented it yet. That's prepared for the next "profile as you run" feaature