pgsql: pg_upgrade: run all data type checks per connection

pg_upgrade: run all data type checks per connection

The checks for data type usage were each connecting to all databases
in the cluster and running their query. On clusters which have a lot
of databases this can become unnecessarily expensive. This moves the
checks to run in a single connection instead to minimize setup and
teardown overhead.

Reviewed-by: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Reviewed-by: Justin Pryzby <pryzby(at)telsasoft(dot)com>
Reviewed-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Discussion: https://postgr.es/m/BB4C76F-D416-4F9F-949E-DBE950D37787@yesql.se

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/347758b1206364e3bec5ad6cd649b4ba9fe1be7b

Modified Files
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src/bin/pg_upgrade/check.c | 749 ++++++++++++++++++++++++++--------------
src/bin/pg_upgrade/pg_upgrade.h | 13 +-
src/bin/pg_upgrade/version.c | 265 +-------------
3 files changed, 506 insertions(+), 521 deletions(-)