pgsql: Teach genbki.pl to auto-generate pg_type entries for array types

Teach genbki.pl to auto-generate pg_type entries for array types.

This eliminates some more tedium in adding new catalog entries,
specifically the need to set up an array type when adding a new
built-in data type. Now it's sufficient to assign an OID for the
array type and write it in an "array_type_oid" metadata field.
You don't have to fill the base type's typarray link explicitly, either.

No catversion bump since the contents of pg_type aren't changed.
(Well, their order might be different, but that doesn't matter.)

John Naylor, reviewed and whacked around a bit by
Dagfinn Ilmari Mannsåker, and some more by me.

Discussion: https://postgr.es/m/CAJVSVGVTb6m9pJF49b3SuA8J+T-THO9c0hxOmoyv-yGKh-FbNg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3dc820c43e427371b66d217f2bd5481fc9ef2e2d

Modified Files
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doc/src/sgml/bki.sgml | 52 +-
src/backend/catalog/Catalog.pm | 78 ++-
src/backend/catalog/genbki.pl | 2 +
src/include/catalog/genbki.h | 2 +
src/include/catalog/pg_type.dat | 864 +++++++++----------------------
src/include/catalog/pg_type.h | 30 +-
src/include/catalog/reformat_dat_file.pl | 29 +-
7 files changed, 415 insertions(+), 642 deletions(-)