Purge long-obsolete fields from State file
There are some fields in the state file that are so obsolete, we no longer update them to newer versions with current version of Tor. If you find that you have one of these in your state file, Tor will keep it around for you forever, since the state file format is intended to preserve unrecognized fields.
We should make our code delete state fields that are known to have been obsolete for a very long time, to avoid possible information leakage.