Migrate config files used by old VSD/GPD installations

Old VSD/GPD installations used a different GenericConfigLocation.
Moreover, we have to rename the application's main config file and
state config file if a custom application name is used (as done for VSD
and GPD).

(cherry picked from commit 2e3e7f2cc43d95c2c753e15e937d0cc78199de0e)

• GnuPG-bug-id: T7700