pgsql: Remove arbitrary FUNC_MAX_ARGS limit in int2vectorin and oidvect

Remove arbitrary FUNC_MAX_ARGS limit in int2vectorin and oidvectorin.

int2vectorin limited the number of array elements it'd take to
FUNC_MAX_ARGS, which is probably fine for the traditional use-cases.
But now that pg_publication_rel.prattrs is an int2vector, it's not
fine at all: it's easy to construct cases where that can have up to
about MaxTupleAttributeNumber entries.  Trying to replicate such
tables leads to logical-replication failures.

As long as we have to touch this code anyway, let's just remove
the a-priori limit altogether, and let it accept any size that'll
be allowed by repalloc.  (Note that since int2vector isn't toastable,
we cannot store arrays longer than about BLCKSZ/2; but there is no
good excuse for letting int2vectorin depend on that.  Perhaps we
will lift the no-toast restriction someday.)

While at it, also improve the equivalent logic in oidvectorin.
I don't know of any practical use-case for long oidvectors right
now, but doing it right actually makes the code shorter.

Per report from Erik Rijkers.  Back-patch to v15 where
pg_publication_rel.prattrs was added.

Discussion: https://postgr.es/m/668ba539-33c5-8190-ca11-def2913cb94b@xs4all.nl

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/db9127c58cbaa748d00055ce10c6bf50a7fbcc1e

Modified Files
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src/backend/utils/adt/int.c | 26 +++++++++++---------------
src/backend/utils/adt/oid.c | 25 +++++++++++--------------
2 files changed, 22 insertions(+), 29 deletions(-)