pgsql: pg_upgrade: Add --set-char-signedness to set the default char si

pg_upgrade: Add --set-char-signedness to set the default char signedness of new cluster.

This change adds a new option --set-char-signedness to pg_upgrade. It
enables user to set arbitrary signedness during pg_upgrade. This helps
cases where user who knew they copied the v17 source cluster from
x86 (signedness=true) to ARM (signedness=false) can pg_upgrade
properly without the prerequisite of acquiring an x86 VM.

Reviewed-by: Noah Misch <noah(at)leadboat(dot)com>
Discussion: https://postgr.es/m/CB11ADBC-0C3F-4FE0-A678-666EE80CBB07%40amazon.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1aab6805919b84a2f2477132d96f2147ed36150e

Modified Files
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doc/src/sgml/ref/pgupgrade.sgml | 53 +++++++++++++++++++++++++++++
src/bin/pg_upgrade/check.c | 12 +++++++
src/bin/pg_upgrade/option.c | 12 +++++++
src/bin/pg_upgrade/pg_upgrade.c | 10 ++++--
src/bin/pg_upgrade/pg_upgrade.h | 3 ++
src/bin/pg_upgrade/t/005_char_signedness.pl | 17 +++++++++
6 files changed, 105 insertions(+), 2 deletions(-)