tests

test: add Postgres MCP tests #4670

Job	Run time
unit tests (3.13)	1m 2s
unit tests (3.9)	1m 1s
integration tests (macos-latest, 3.13)	1m 24s
integration tests (ubuntu-latest, 3.9)	1m 22s
integration tests (windows-latest, 3.13)	1m 54s
integration tests (macos-latest, 3.9)	1m 40s
integration tests (windows-latest, 3.9)	1m 58s
integration tests (ubuntu-latest, 3.13)	49s
	11m 10s

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