Verify and support all system tables in pgproto

It's important to be able to work with system tables from pgproto. However, some of these tables contain unsupported values, resulting in unsupported type errors. We should add tests that involve reading from them in order to verify support of them or to find new errors.

Note: #731 (closed) and #729 (closed)

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changed milestone to %24.6 - Plugins and Tiers

assigned to @UngiftedPoet

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Done: see test_select_from_system_tables

closed

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closed

changed milestone to %24.5 - Lowercase