pgsql: Fix pgbench timestamp bugs.

Fix pgbench timestamp bugs.

Commit 547f04e changed pgbench to use microsecond accounting, but
introduced a couple of logging and aggregation bugs:

1. We print Unix epoch timestamps so that you can correlate them with
other logs, but these were inadvertently changed to use a
system-dependent reference epoch. Compute Unix timestamps, and begin
aggregation intervals on the boundaries of whole Unix epoch seconds, as
before.

2. The user-supplied aggregation interval needed to be scaled.

Back-patch to 14.

Author: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Author: Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>
Author: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
Reported-by: YoungHwan Joo <rulyox(at)gmail(dot)com>
Reported-by: Gregory Smith <gregsmithpgsql(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAF7igB1r6wRfSCEAB-iZBKxkowWY6%2BdFF2jObSdd9%2BiVK%2BvHJg%40mail.gmail.com
Discussion: https://postgr.es/m/CAHLJuCW_8Vpcr0%3Dt6O_gozrg3wXXWXZXDioYJd3NhvKriqgpfQ%40mail.gmail.com

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/5614a0f78eaaa51c07bd753ca854de238c730b84

Modified Files
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src/bin/pgbench/pgbench.c | 43 ++++++++++++++++++++++++++++++++++---------
1 file changed, 34 insertions(+), 9 deletions(-)