MEDIUM: stats: add persistent state to typed output format

MEDIUM: stats: add persistent state to typed output format

Add a fourth character to the second column of the "typed output format"
to indicate whether the value results from a volatile or persistent metric
('V' or 'P' characters respectively). A persistent metric means the value
could possibily be preserved across reloads by leveraging a shared memory
between multiple co-processes. Such metrics are identified as "shared" in
the code (since they are possibly shared between multiple co-processes)

Some reg-tests were updated to take that change into account, also, some
outputs in the configuration manual were updated to reflect current
behavior.