Upgrade PostgreSQL clusters up to 11

Our PostgreSQL clusters should be upgraded to PostgreSQL 11. This ticket tracks the progress of this operation.

Documentation for pg_upgrade : https://www.postgresql.org/docs/11/pgupgrade.html

Clusters to upgrade:

Primary

• prado/main (softwareheritage)
• prado/secondary (scheduler, etc.)
• prado/hdd
• somerset/indexer
• somerset/testdedup

Physical replica (follow step 10 of the pgupgrade docs)

• dbreplica1.euwest.azure/indexer (replica of somerset/indexer)

Ignored until upgrade of prado/main (#1534 (closed))

• somerset/replica
• dbreplica0.euwest.azure/replica

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Migrated from T1591 (view on Phabricator)