vppapigen: crcchecker: report in-progress messages

vppapigen: crcchecker: report in-progress messages

in-progress messages do not give any API stability guarantees,
by design, to allow easy iteration. Provide an easy way
to know which messages are in-progress.

If as a user you see "in-progress" message that you want
to use in production, please contact the feature owner
and discuss the path to removing the "in-progress" status
before that.

Change-Id: I27729995e26a70af373e642b871dbb5cc5526959
Type: improvement
Signed-off-by: Andrew Yourtchenko <ayourtch@gmail.com>