Fwd: Emit namespace in post-copy output

When running a VACUUM or CLUSTER command, the namespace name is not part of
the emitted message.

Using `vacuumdb` CLI tool recently with multiple jobs, I found that
reading the output messages harder to match the relations with their
namespaces.

Example:

INFO: vacuuming "sendgrid.open"
INFO: vacuuming "mailgun.open"
...
INFO: "open": found 0 removable, 31460776 nonremovable row versions in
1358656 pages
DETAIL: 0 dead row versions cannot be removed yet.
CPU 31.35s/261.26u sec elapsed 1620.68 sec.
...

In this example. the user can't readily tell which `open` relation was
completed.

Attached is a patch using existing functions to include the namespace in
the output string.

Looking forward to feedback!
-Mike Fiedler