actions: Omit table number when possible for formatting "next" action.

actions: Omit table number when possible for formatting "next" action.

Until now, formatting the "next" action has always required including
the table number, because the action struct didn't include enough context
so that the formatter could decide whether the table number was the next
table or some other table.  This is more or less OK, but an upcoming commit
will add a "pipeline" field to the "next" action, which means that the same
policy there would require that the pipeline always be printed.  That's a
little obnoxious because 99+% of the time, the pipeline to be printed is
the same pipeline that the flow is in and printing it would be distracting.
So it's better to store some context to help with formatting.  This commit
begins adopting that policy for the existing table number field.

Signed-off-by: Ben Pfaff <blp@ovn.org>
Acked-by: Mickey Spiegel <mickeys.dev@gmail.com>