Extract WalProposer into the neon extension (#2217)

Including, but not limited to:

* Fixes to neon management code to support walproposer-as-an-extension

* Fix issue in expected output of pg settings serialization.

* Show the logs of a failed --sync-safekeepers process in CI

* Add compat layer for renamed GUCs in postgres.conf

* Update vendor/postgres to the latest origin/main

test_runner/batch_others/test_wal_acceptor.py

@@ -569,7 +569,7 @@ class ProposerPostgres(PgProtocol):
                 f"neon.timeline_id = '{self.timeline_id.hex}'\n",
                 f"neon.tenant_id = '{self.tenant_id.hex}'\n",
                 f"neon.pageserver_connstring = ''\n",
-                f"safekeepers = '{safekeepers}'\n",
+                f"neon.safekeepers = '{safekeepers}'\n",
                 f"listen_addresses = '{self.listen_addr}'\n",
                 f"port = '{self.port}'\n",
             ]