pgsql: Add support for toast_value_type=oid8

Add support for toast_value_type=oid8

This commit adds the possibility to define TOAST tables with oid8 as
their chunk_id, based on the reloption toast_value_type. All the
external TOAST pointers still rely on varatt_external_oid and a single
vartag. The values inserted in the oid8 TOAST tables are fed from the
OID8 value generator, casted to OID for now, as we do not have a
vartag_external able to store Oid8 values yet.

An upcoming commit will add support for a new vartag_external and its
associated structures, with the code being able to use a different
on-disk external TOAST pointer depending on the attribute type of
chunk_id defined in TOAST relations.

All the changes done here are mechanical, mostly around the TOAST code
that needs to be able to do chunk_id lookups based on the two types now
supported.

Bump catalog version.

Author: Michael Paquier <michael(at)paquier(dot)xyz>
Reviewed-by: Greg Burd <greg(at)burd(dot)me>
Reviewed-by: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Reviewed-by: Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp>
Discussion: https://postgr.es/m/af19kUjwjhaoUTLn@paquier.xy

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a625fc570c22e199471e1a2656e2c32b8dc0c0fd

Modified Files
--------------
contrib/amcheck/verify_heapam.c | 13 ++--
doc/src/sgml/ref/create_table.sgml | 5 +-
doc/src/sgml/storage.sgml | 7 +-
src/backend/access/common/reloptions.c | 3 +-
src/backend/access/common/toast_internals.c | 88 +++++++++++++++++--------
src/backend/access/heap/heaptoast.c | 7 +-
src/backend/catalog/toasting.c | 25 ++++++-
src/backend/replication/logical/reorderbuffer.c | 9 ++-
src/include/access/toast_internals.h | 4 ++
src/include/catalog/pg_opclass.dat | 3 +-
src/include/utils/rel.h | 1 +
src/test/regress/expected/reloptions.out | 15 ++++-
src/test/regress/sql/reloptions.sql | 8 +++
13 files changed, 142 insertions(+), 46 deletions(-)