pgsql: Document the 'command' column of pg_stat_progress_repack

Document the 'command' column of pg_stat_progress_repack

Commit ac58465e0618 added and documented a new progress-report view for
REPACK, but neglected to list the 'command' column in the docs. This is
my (Álvaro's) fail, as I added the column in v23 of the patch and forgot
to document it.

In passing, add a note in the docs for pg_stat_progress_cluster that it
might contain rows for sessions running REPACK, though mapping the
command name to either the older commands; and that it is for backwards-
compatibility only. (Maybe we should just remove this older view.)

Author: Noriyoshi Shinoda <noriyoshi(dot)shinoda(at)hpe(dot)com>
Discussion: https://postgr.es/m/LV8PR84MB37870F0F35EF2E8CB99768CBEE47A@LV8PR84MB3787.NAMPRD84.PROD.OUTLOOK.COM
Discussion: https://postgr.es/m/202510101352.vvp4p3p2dblu@alvherre.pgsql

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a630ac5c2016e523a1c29df117b7c1a563a7f6f8

Modified Files
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doc/src/sgml/monitoring.sgml | 28 ++++++++++++++++++++++------
1 file changed, 22 insertions(+), 6 deletions(-)