pgsql: amcheck: Use correct varlena size accessor in bt_normalize_tuple

amcheck: Use correct varlena size accessor in bt_normalize_tuple()

bt_normalize_tuple() uses VARSIZE() to get the size of varlena, even though
it's not yet known, that it has a 4-byte header. Fix this by replacing a
accessor with a universal VARSIZE_ANY().

Backpatch to all supported versions.

Reported-by: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://postgr.es/m/7ckc7oka4bvafkf5bwlqs6ygrhlsbhz25ppozfch7zbuxcx3rf%40e4pr4oqenalc
Author: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
Reviewed-by: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
Backpatch-through: 14

Branch
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REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/8abb8a1555f4051491eced0307adf218e0f9f34e

Modified Files
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contrib/amcheck/verify_nbtree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)