Fwd: Emit namespace in post-copy output

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