RE: [PoC] pg_upgrade: allow to upgrade publisher node

Hi,

The BF animal fairywren[1] failed when testing
003_upgrade_logical_replication_slots.pl.

From the log, I can see pg_upgrade failed to open the
invalid_logical_replication_slots.txt:

# Checking for valid logical replication slots                  
# could not open file
"C:/tools/nmsys64/home/pgrunner/bf/root/HEAD/pgsql.build/testrun/pg_upgrade/003_upgrade_logical_replication_slots/data/t_003_upgrade_logical_replication_slots_new_publisher_data/pgdata/pg_upgrade_output.d/20231026T112558.309/invalid_logical_replication_slots.txt":
Nosuch file or directory
 
# Failure, exiting

The reason could be the length of this path(262) exceed the windows path
limit(260 IIRC). If so, I recall we fixed similar things before (e213de8e7) by
reducing the path somehow.

In this case, I think one approach is to reduce the file and testname to
xxx_logical_slots instead of xxx_logical_replication_slots. But we will analyze more
and share fix soon.

[1] https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=fairywren&dt=2023-10-26%2009%3A04%3A54

Best Regards,
Hou zj