Enable libpq-compatible "postgresql" URL schemes #206

Job	Run time
code-coverage	3m 41s
linux-unit (postgres:15, swift:5.7-jammy)	2m 46s
linux-unit (postgres:15, swift:5.8-jammy)	3m 23s
linux-unit (postgres:15, swiftlang/swift:nightly-5.9-jammy)	4m 1s
linux-unit (postgres:15, swiftlang/swift:nightly-main-jammy)	4m 30s
linux-unit (postgres:13, swift:5.7-jammy)	3m 44s
linux-unit (postgres:13, swift:5.8-jammy)	3m 20s
linux-unit (postgres:13, swiftlang/swift:nightly-5.9-jammy)	3m 54s
linux-unit (postgres:13, swiftlang/swift:nightly-main-jammy)	4m 12s
linux-unit (postgres:11, swift:5.7-jammy)	3m 27s
linux-unit (postgres:11, swift:5.8-jammy)	2m 58s
linux-unit (postgres:11, swiftlang/swift:nightly-5.9-jammy)	3m 53s
linux-unit (postgres:11, swiftlang/swift:nightly-main-jammy)	4m 13s
api-breakage	4m 57s
gh-codeql (ubuntu-latest)	6m 17s
gh-codeql (macos-13)	8m 12s
linux-integration	4m 33s
macos-unit (~14.3)	3m 13s
macos-unit (15.0-beta)	3m 28s
	1h 18m 42s

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