pgsql: Fix wrong logic in TransactionIdInRecentPast()

Fix wrong logic in TransactionIdInRecentPast()

The TransactionIdInRecentPast() should return false for all the transactions
older than TransamVariables->oldestClogXid.  However, the function contains
a bug in comparison FullTransactionId to TransactionID allowing full
transactions between nextXid - 2^32 and oldestClogXid - 2^31.

This commit fixes TransactionIdInRecentPast() by turning the oldestClogXid into
FullTransactionId first, then performing the comparison.

Backpatch to all supported versions.

Reported-by: Egor Chindyaskin
Bug: 18212
Discussion: https://postgr.es/m/18212-547307f8adf57262%40postgresql.org
Author: Karina Litskevich
Reviewed-by: Kyotaro Horiguchi
Backpatch-through: 12

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/e3e05addee42c643867557a3065debb085f1d169

Modified Files
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src/backend/utils/adt/xid8funcs.c | 30 +++++++++++++++++++-----------
1 file changed, 19 insertions(+), 11 deletions(-)