Problem: The "Scanning:" completion, bufwrite, and indent (there may be
more) messages which indicate progress can use the "progress" kind
for their msg_show event. Indent message does not have a kind.
Solution: Emit these messages with the "progress" kind. Set the message id
to the replaced kind so that a UI knows to replace it (and to provide
a migration path in case a UI was distinguishing these messages for
whatever reason).
ff68fd6b8a
