Expose query `metadata` in `PostgresRowSequence` #1305

Job	Run time
api-breakage	4m 10s
macos-all (postgresql@16, scram-sha-256, ~14.3)	6m 24s
linux-integration-and-dependencies (postgres:16)	9m 5s
linux-unit (swift:5.8-jammy)	2m 29s
macos-all (postgresql@16, scram-sha-256, ~15)	2m 22s
linux-integration-and-dependencies (postgres:14)	8m 53s
linux-unit (swift:5.9-jammy)	2m 39s
linux-integration-and-dependencies (postgres:12)	8m 48s
linux-unit (swift:5.10-noble)	3m 22s
linux-unit (swiftlang/swift:nightly-6.0-jammy)	3m 35s
linux-unit (swiftlang/swift:nightly-main-jammy)	3m 58s
	55m 45s

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