[PostGIS] #5995: Add pg_upgrade testing in CI

[PostGIS]

#5995: Add pg_upgrade testing in CI
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 Reporter:  strk          |      Owner:  robe
     Type:  task          |     Status:  new
 Priority:  medium        |  Milestone:  PostGIS 3.7.0
Component:  QA/buildbots  |    Version:  master
 Keywords:  pg_upgrade    |
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 At the moment we have no CI agent testing pg_upgrade.
 The OCI image used for Woodie testing already contains different
 PostgreSQL versions so would be usable for such test.

 Ideally we'd have a script to do the testing, so developers can also
 easily run the script locally, like utils/check_all_upgrades.sh (and
 possibly adding the new support in that same script)

 Known bug whose fix could be secured in this way: #5899
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Ticket URL: <https://trac.osgeo.org/postgis/ticket/5995>
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