Compatibility with PostgreSQL 14 (#1926)

PostgreSQL 14 changed the behavior of replicas when certain parameters (like for example `max_connections`) are changed (increased): https://github.com/postgres/postgres/commit/15251c0a.
Instead of immediately exiting Postgres 14 pauses replication and waits for actions from the operator.

Since the `pg_is_wal_replay_paused()` returning `True` is the only indicator of such a change, Patroni on the replica will call the `pg_wal_replay_resume()`, which would cause either continue replication or shutdown (like previously).

So far Patroni was never calling `pg_wal_replay_resume()` on its own, therefore, to remain backward compatible it will call it only for PostgreSQL 14+.

.github/workflows/run_tests.py

@@ -23,7 +23,9 @@ def main():
 
     env = os.environ.copy()
     if sys.platform.startswith('linux'):
-        version = {'etcd': '9.6', 'etcd3': '13', 'consul': 12, 'exhibitor': 11, 'kubernetes': 13, 'raft': 12}.get(what)
+        from mapping import versions
+
+        version = versions.get(what)
         path = '/usr/lib/postgresql/{0}/bin:.'.format(version)
         unbuffer = ['timeout', '600', 'unbuffer']
         args = ['--tags=-skip'] if what == 'etcd' else []