GenBKI emits useless open;close for catalogs without rows

Hi,

Whilst looking at PostgreSQL's bootstrapping process, I noticed that
postgres.bki contains quite a few occurrances of the pattern "open
$catname; close $catname".
I suppose this pattern isn't too expensive, but according to my
limited research a combined open+close cycle doens't do anything
meaningful, so it does waste some CPU cycles in the process.

The attached patch 1 removes the occurances of those combined
open/close statements in postgresql.bki. Locally it passes
check-world, so I assume that opening and closing a table is indeed
not required for initializing a data-less catalog during
bootstrapping.

A potential addition to the patch would to stop manually closing
relations: initdb and check-world succeed without manual 'close'
operations because the 'open' command auto-closes the previous open
relation (in boot_openrel). Testing also suggests that the last opened
relation apparently doesn't need closing - check-world succeeds
without issues (incl. with TAP enabled). That is therefore implemented
in attached patch 2 - it removes the 'close' syntax in its entirety.

Kind regards,

Matthias van de Meent
Neon (https://neon.tech)